Light-emitting element, lighting device, light-emitting device, and electronic device

ABSTRACT

A light-emitting element whose degree of deterioration with driving time is improved and of which emission colors are easily controlled. A light-emitting emitting element having a first electrode, a second electrode, and a layer containing an organic compound located between the first electrode and the second electrode, in which the layer containing the organic compound at least has, from the second electrode side, a light-emitting layer in which a first layer, a second layer, and a third layer are stacked, and a hole-transporting layer provided in contact with the third layer; the first layer contains a first organic compound and a second organic compound; the second layer contains a third organic compound and a fourth organic compound; and the third layer contains the first organic compound and a fifth organic compound.

This application is a continuation of copending application Ser. No.15/619,813 filed on Jun. 12, 2017 which is a continuation of applicationSer. No. 14/192,175 filed on Feb. 27, 2014 (now U.S. Pat. No. 9,685,623issued Jun. 20, 2017) which is a continuation of application Ser. No.13/614,151 filed on Sep. 13, 2012 (now U.S. Pat. No. 8,664,849 issuedMar. 4, 2014) which is a continuation of application Ser. No. 12/234,258filed on Sep. 19, 2008 (now U.S. Pat. No. 8,283,856 issued Oct. 9,2012), all of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to a light-emitting element at least partof which includes an organic compound. The present invention alsorelates to a lighting device, a light-emitting device, and an electronicdevice which are provided with the light-emitting element.

2. Description of the Related Art

Development of a light-emitting device in which a layer containing anorganic compound is provided between a pair of electrodes and lightemission is obtained by current flowing between the pair of electrodeshas been advanced. Such a light-emitting device is capable of beingreduced in thickness and weight in comparison with a display devicewhich is currently called a “thin-film display device”. Moreover,because of self-emission type, such a light-emitting device has a highlevel of visibility and high response speed. Therefore, such alight-emitting device has been actively developed as a next-generationdisplay device, and has been partly put into practical use at present.

Such a light-emitting element can emit light of various colors dependingon a material contained in a layer containing an organic compound, whichserves as an emission center. Moreover, by stacking of layers containingan emission center substance which exhibits different emission colors,light emission overlap, and more variations of emission colors can beobtained. In particular, the emphasis is put on white light which can beobtained by overlapping of red light, green light, and blue light oroverlapping of emission colors which are in a relationship ofcomplementary colors because white light is suitable for the use of abacklight or lighting, in addition to a display.

Deterioration of a light-emitting element is given as one of the reasonswhy such a light-emitting device with many advantages is limited to apartial practical use. A light-emitting element is deteriorated suchthat luminance is lowered with accumulation of driving time even if thesame amount of current is fed. In order to promote the light-emittingelement, it is essential to obtain a light-emitting element whose degreeof deterioration is acceptable for an actual product. A light-emittingelement has been researched from many aspects such as aspects of adriver circuit, sealing, an element structure, and a material (forexample, see Patent Document 1: Japanese Published Patent ApplicationNo. 2006-114796) and Patent Document 2: Japanese Published PatentApplication No. 2007-220593).

However, actually, there are various causes of decrease in luminancewith accumulation of driving time, and the present measures are notenough.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a light-emittingelement or a lighting device whose degree of deterioration with drivingtime is improved.

It is another object of the present invention to provide alight-emitting device or an electronic device which has high reliabilityof a display portion.

It is another object of the present invention to provide alight-emitting element or a lighting device of which emission colors areeasily controlled.

It is another object of the present invention to provide alight-emitting device or an electronic device which has high displayquality.

One feature of the present invention is a light-emitting elementincluding a first electrode, a second electrode, and a layer whichcontains an organic compound and is located between the first electrodeand the second electrode. The layer containing the organic compoundincludes at least a light-emitting layer in which a first layer, asecond layer, and a third layer are stacked from the second electrodeside, and a hole-transporting layer provided in contact with the thirdlayer. The first layer contains a first organic compound and a secondorganic compound. The second layer contains a third organic compound anda fourth organic compound. The third layer contains the first organiccompound and a fifth organic compound. The amount of the second organiccompound contained in the first layer is larger than that of the firstorganic compound in the first layer. The amount of the fifth organiccompound contained in the third layer is larger than that of the firstorganic compound in the third layer. Decrease in the luminance of thelight-emitting element of the present invention which has such astructure with accumulation of driving time is small, and thus thereliability of the light-emitting element can be improved. Moreover,emission colors of the light-emitting element can be easily controlled.

Another feature of the present invention is a light-emitting elementincluding a first electrode, a second electrode, and a layer whichcontains an organic compound and is located between the first electrodeand the second electrode. The layer containing the organic compoundincludes at least a layer playing a role of emitting light, in which afirst layer, a second layer, and a third layer are stacked from thesecond electrode side, and a hole-transporting layer provided in contactwith the third layer. The first layer contains a first organic compoundand a second organic compound. The second layer contains a third organiccompound and a fourth organic compound. The third layer contains thefirst organic compound and a fifth organic compound. The proportion ofthe first organic compound in the first layer is greater than or equalto 0.1 wt % and less than 50 wt %. The proportion of the third organiccompound in the second layer is greater than or equal to 0.1 wt % andless than 50 wt %. The proportion of the first organic compound in thethird layer is greater than or equal to 0.1 wt % and less than 50 wt %.Decrease in the luminance of the light-emitting element of the presentinvention which has such a structure with accumulation of driving timeis small, and thus the reliability of the light-emitting element can beimproved. Moreover, emission colors of the light-emitting element can beeasily controlled.

Another feature of the present invention is a light-emitting elementincluding a first electrode, a second electrode, and a layer whichcontains an organic compound and is located between the first electrodeand the second electrode. The layer containing the organic compoundincludes at least a layer playing a role of emitting light, in which afirst layer, a second layer, and a third layer are stacked from thesecond electrode side, and a hole-transporting layer provided in contactwith the third layer. The first layer contains a first organic compoundand a second organic compound. The second layer contains a third organiccompound and a fourth organic compound. The third layer contains thefirst organic compound and a fifth organic compound. The proportion ofthe first organic compound in the first layer is greater than or equalto 0.1 wt % and less than 50 wt %. The proportion of the third organiccompound in the second layer is greater than or equal to 0.1 wt % andless than 50 wt %. The proportion of the first organic compound in thethird layer is greater than or equal to 0.1 wt % and less than 50 wt %.Light is emitted from the first organic compound and the third organiccompound when voltage is applied between the first electrode and thesecond electrode so that the potential of the first electrode becomeshigher than that of the second electrode. Decrease in the luminance ofthe light-emitting element of the present invention which has such astructure with accumulation of driving time is small, and thus thereliability of the light-emitting element can be improved. Moreover,emission colors of the light-emitting element can be easily controlled.

Another feature of the present invention is a light-emitting elementincluding a first electrode, a second electrode, and a layer whichcontains an organic compound and is located between the first electrodeand the second electrode. The layer containing the organic compoundincludes at least a layer playing a role of emitting light, in which afirst layer, a second layer, and a third layer are stacked from thesecond electrode side, and a hole-transporting layer provided in contactwith the third layer. The first layer contains a first organic compoundand a second organic compound. The second layer contains a third organiccompound and a fourth organic compound. The third layer contains thefirst organic compound and a fifth organic compound. The proportion ofthe first organic compound in the first layer is greater than or equalto 0.1 wt % and less than 50 wt %. The proportion of the third organiccompound in the second layer is greater than or equal to 0.1 wt % andless than 50 wt %. The proportion of the first organic compound in thethird layer is greater than or equal to 0.1 wt % and less than 50 wt %.The first organic compound is an emission center substance in the firstlayer and the third layer. The third organic compound is an emissioncenter substance in the second layer. Decrease in the luminance of thelight-emitting element of the present invention which has such astructure with accumulation of driving time is small, and thus thereliability of the light-emitting element can be improved. Moreover,emission colors of the light-emitting element can be easily controlled.

Another feature of the present invention is a light-emitting element inwhich the fourth organic compound and the fifth organic compound are amaterial having a hole-transporting property and the second organiccompound is a material having an electron-transporting property in theabove-described structures. Decrease in the luminance of thelight-emitting element of the present invention which has such astructure with accumulation of driving time is small, and thus thereliability of the light-emitting element can be improved. Moreover,emission colors of the light-emitting element can be easily controlled.

Another feature of the present invention is a light-emitting element inwhich the fourth organic compound is a condensed polycyclic substance inthe above-described structures. In the light-emitting element of thepresent invention which has such a structure, the condensed polycyclicsubstance which has a wide band gap and is suitable as a host materialis used as a host of an emission center substance, and decrease in theluminance with accumulation of driving time is small; thus, thereliability of the light-emitting element can be improved. Moreover,emission colors of the light-emitting element can be easily controlled.

Another feature of the present invention is a light-emitting element inwhich the fourth organic compound is a tricyclic, tetracyclic,pentacyclic, or hexacyclic condensed polycyclic aromatic compound in theabove-described structures. In the light-emitting element of the presentinvention which has such a structure, a tricyclic, tetracyclic,pentacyclic, or hexacyclic condensed polycyclic aromatic compound whichhas a wide band gap and is suitable as a host material is used as a hostof an emission center substance, and decrease in the luminance withaccumulation of driving time is small; thus, the reliability of thelight-emitting element can be improved. Moreover, emission colors of thelight-emitting element can be easily controlled.

Another feature of the present invention is a light-emitting element inwhich the fourth organic compound is an anthracene derivative in theabove-described structures. In the light-emitting element of the presentinvention which has such a structure, the anthracene derivative whichhas a wide band gap and is suitable as a host material is used as a hostof an emission center substance, and decrease in the luminance withaccumulation of driving time is small; thus, the reliability of thelight-emitting element can be improved. Moreover, emission colors of thelight-emitting element can be easily controlled.

Another feature of the present invention is a light-emitting element inwhich the fourth organic compound and the fifth organic compound are thesame substance in the above-described structures. The light-emittingelement of the present invention which has such a structure has thefeatures of the above-described structures, and further can bemanufactured by a simplified process.

Another feature of the present invention is a light-emitting element inwhich a peak wavelength of light emitted from the first organic compoundis shorter than that of light emitted from the third organic compound inthe above-described structures. The light-emitting element of thepresent invention which has such a structure has the features of theabove-described structures, and further emission colors can be easilycontrolled.

Another feature of the present invention is a light-emitting element inwhich a color of light emitted from the first organic compound and acolor of light emitted from the third organic compound are in arelationship of complementary colors in the above-described structures.The light-emitting element of the present invention which has such astructure has the features of the above-described structures, andfurther white light emission can be obtained. The light-emitting elementof the present invention of which emission colors can be easilycontrolled can be preferably applied to a white light-emitting element.

Another feature of the present invention is a light-emitting element inwhich the first organic compound emits blue light and the third organiccompound emits yellow light in the above-described structures. Thelight-emitting element of the present invention which has such astructure has the features of the above-described structures, andfurther white light emission can be obtained. The light-emitting elementof the present invention of which emission colors can be easilycontrolled can be preferably applied to a white light-emitting element.

Another feature of the present invention is a light-emitting element inwhich a peak wavelength of light emitted from the first organic compoundis in the range of 400 nm to 480 nm and a peak wavelength of lightemitted from the third organic compound is in the range of 540 nm to 600nm. The light-emitting element of the present invention which has such astructure has the features of the above-described structures, and whitelight emission can be obtained. The light-emitting element of thepresent invention of which emission colors can be easily controlled canbe preferably applied to a white light-emitting element.

Another feature of the present invention is a light-emitting element inwhich the first organic compound emits blue green light and the thirdorganic compound emits red light in the above-described structure. Thelight-emitting element of the present invention which has such astructure has the features of the above-described structures, and whitelight emission can be obtained. The light-emitting element of thepresent invention of which emission colors can be easily controlled canbe preferably applied to a white light-emitting element.

Another feature of the present invention is a light-emitting element inwhich a peak wavelength of light emitted from the first organic compoundis in the range of 480 nm to 520 nm and a peak wavelength of lightemitted from the third organic compound is in the range of 600 nm to 700nm. The light-emitting element of the present invention which has such astructure has the features of the above-described structures, and whitelight emission can be obtained. The light-emitting element of thepresent invention of which emission colors can be easily controlled canbe preferably applied to a white light-emitting element.

Another feature of the present invention is a lighting device in whichthe above-described light-emitting element is used. The lighting devicewhich has such a structure can be a lighting device with little decreasein luminance with accumulation of driving time and long life. Moreover,emission colors can be easily controlled, and thus emission colorscorresponding to the purpose of the lighting device can be easilyprovided.

Another feature of the present invention is a light-emitting devicewhich is provided with a light-emitting element and a unit forcontrolling emission of the light-emitting element. The light-emittingdevice which has such a structure can be a light-emitting device withlittle decrease in luminance with accumulation of driving time and longlife. Moreover, emission colors can be easily controlled, and thus thelight-emitting device can have high display quality.

Another feature of the present invention is an electronic device inwhich the above-described light-emitting device is mounted on a displayportion. The electronic device which has such a structure can be anelectronic device having a display portion with long life. Moreover,emission colors can be easily controlled, and thus the electronic devicecan have a display portion with high display quality.

The present invention makes it possible to provide a light-emittingelement whose degree of deterioration with driving time can be improved.

In addition, a lighting device whose degree of deterioration withdriving drive is improved can be provided.

Further, a light-emitting device or an electronic device which has adisplay portion with high reliability can be provided.

Moreover, a light-emitting element or a lighting device of whichemission colors can be easily controlled can be provided.

Furthermore, a light-emitting device or an electronic device with highdisplay quality can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIG. 1 is a schematic view of a light-emitting element of the presentinvention;

FIG. 2 is a schematic view of a conventional light-emitting element;

FIG. 3A is a top view of a light-emitting device of the presentinvention and FIG. 3B is a cross-sectional view of the same;

FIG. 4A is a perspective view of a light-emitting device of the presentinvention and FIG. 4B is a cross-sectional view of the same;

FIGS. 5A to 5D are diagrams showing electronic devices of the presentinvention;

FIG. 6 is a diagram showing an electronic device of the presentinvention;

FIG. 7 is a diagram showing an electronic device of the presentinvention;

FIG. 8 is a diagram showing an electronic device of the presentinvention;

FIG. 9 is a graph showing current density-luminance characteristics of alight-emitting element 1;

FIG. 10 is a graph showing luminance-current efficiency characteristicsof a light-emitting element 1;

FIG. 11 is a graph showing voltage-luminance characteristics of alight-emitting element 1;

FIG. 12 is a graph showing voltage-current characteristics of alight-emitting element 1;

FIG. 13 is a graph showing an emission spectrum of a light-emittingelement 1;

FIG. 14 is a graph showing current density-luminance characteristics ofa light-emitting element 2;

FIG. 15 is a graph showing luminance-current efficiency characteristicsof a light-emitting element 2;

FIG. 16 is a graph showing voltage-luminance characteristics of alight-emitting element 2;

FIG. 17 is a graph showing voltage-current characteristics of alight-emitting element 2;

FIG. 18 is a graph showing an emission spectrum of a light-emittingelement 2;

FIG. 19 is a graph showing an emission spectrum of a light-emittingelement 3;

FIG. 20 is a graph showing time dependence of normalized luminance of alight-emitting element 1 and a light-emitting element 3;

FIG. 21 is a graph showing current density-luminance characteristics ofa light-emitting element 4;

FIG. 22 is a graph showing luminance-current efficiency characteristicsof a light-emitting element 4;

FIG. 23 is a graph showing voltage-luminance characteristics of alight-emitting element 4;

FIG. 24 is a graph showing voltage-current characteristics of alight-emitting element 4;

FIG. 25 is a graph showing an emission spectrum of a light-emittingelement 4;

FIG. 26 is a graph showing current density-luminance characteristics ofa light-emitting element 5;

FIG. 27 is a graph showing luminance-current efficiency characteristicsof a light-emitting element 5;

FIG. 28 is a graph showing voltage-luminance characteristics of alight-emitting element 5;

FIG. 29 is a graph showing voltage-current characteristics of alight-emitting element 5;

FIG. 30 is a graph showing an emission spectrum of a light-emittingelement 5;

FIG. 31 is a graph showing an emission spectrum of a light-emittingelement 6;

FIG. 32 is a graph showing time dependence of normalized luminance of alight-emitting element 4 and a light-emitting element 6;

FIG. 33 is a graph showing current density-luminance characteristics ofa light-emitting element 7;

FIG. 34 is a graph showing luminance-current efficiency characteristicsof a light-emitting element 7;

FIG. 35 is a graph showing voltage-luminance characteristics of alight-emitting element 7;

FIG. 36 is a graph showing voltage-current characteristics of alight-emitting element 7;

FIG. 37 is a graph showing an emission spectrum of a light-emittingelement 7;

FIG. 38 is a graph showing current density-luminance characteristics ofa light-emitting element 8;

FIG. 39 is a graph showing luminance-current efficiency characteristicsof a light-emitting element 8;

FIG. 40 is a graph showing voltage-luminance characteristics of alight-emitting element 8;

FIG. 41 is a graph showing voltage-current characteristics of alight-emitting element 8; and

FIG. 42 is a graph showing an emission spectrum of a light-emittingelement 8.

DETAILED DESCRIPTION OF THE INVENTION

Embodiment Modes of the present invention will be hereinafter describedwith reference to the accompanying drawings. Note that the presentinvention can be implemented in many different modes and it is easilyunderstood by those skilled in the art that modes and details of thepresent invention can be modified in various ways without departing fromthe purpose and scope of the present invention. Therefore, the presentinvention should not be interpreted as being limited to the descriptionbelow of Embodiment Modes.

Embodiment Mode 1

FIG. 2 is a schematic view of a conventional light-emitting element 115corresponding to the present invention. The light-emitting element 115has a structure in which a layer 116 containing an organic compound isprovided between a first electrode 111 and a second electrode 110. Inthe layer 116 containing the organic compound, a second layer 113 and afirst layer 112 are stacked in this order from the first electrode 111side, and a hole-transporting layer 114 is provided in contact with thesecond layer 113. The first layer 112 contains a first organic compoundwhich serves as an emission center and a second organic compound as ahost material which disperses the first organic compound. The secondlayer 113 contains a third organic compound which serves as an emissioncenter and a fourth organic compound as a host material which dispersesthe third organic compound. The second organic compound is formed of amaterial having an electron-transporting property. The fourth organiccompound is formed of a material having a hole-transporting property.Note that in this specification, the words “having anelectron-transporting property” mean that at least anelectron-transporting property is higher than a hole-transportingproperty, and the words “having a hole-transporting property” mean thatat least a hole-transporting property is higher than anelectron-transporting property. The hole-transporting layer 114 isprovided for a space between the electrodes and the layer which emitslight and is formed of a material having a hole-transporting property.

In the light-emitting element 115, when voltage is applied between thefirst electrode 111 and the second electrode 110 so that the potentialof the first electrode 111 becomes higher than that of the secondelectrode 110, electrons are injected from the second electrode 110 tothe layer 116 containing the organic compound and holes are injectedfrom the first electrode 111 to the layer 116 containing the organiccompound. Most of the injected carriers are recombined in the vicinityof an interface between the first layer 112 and the second layer 113 andthe first organic compound and the third organic compound emit light,whereby light emission in which the two emission spectrums overlap canbe obtained. Note that in the layer 116 containing the organic compound,a layer may be provided or is not necessarily provided as appropriatebetween the second electrode 110 and the first layer 112 and between thefirst electrode 111 and the hole-transporting layer 114

The inventor found that in such a light-emitting element 115, the degreeof deterioration of the light-emitting element with driving time can beimproved when the third layer containing the first organic compoundwhich is an emission center substance contained in the first layer 112and the fifth organic compound as a host material dispersing the firstorganic compound is provided between the second layer 113 and thehole-transporting layer 114.

FIG. 1 is a schematic view of a light-emitting element 106 of thisembodiment mode. Between a first electrode 101 and a second electrode100, a third layer 104, a second layer 103, and a first layer 102 arestacked from the first electrode 101 side. Moreover, a hole-transportinglayer 105 is provided in contact with the third layer 104. The firstlayer 102 contains a first organic compound which serves as an emissioncenter and a second organic compound as a host material which dispersesthe first organic compound. The second layer 103 contains a thirdorganic compound which serves as an emission center and a fourth organiccompound as a host material which disperses the third organic compound.The third layer 104 contains a first organic compound which serves as anemission center and a fifth organic compound as a host material whichdisperses the first organic compound. Here, the first organic compoundin the first layer 102 and the first organic compound in the third layer104 are the same substance. The second organic compound is formed of amaterial having an electron-transporting property, and the fourthorganic compound is formed of a material having a hole-transportingproperty.

Also in the light-emitting element 106, similarly to in thelight-emitting element 115, when voltage is applied between the firstelectrode 101 and the second electrode 100 so that the potential of thefirst electrode 101 becomes higher than that of the second electrode100, and light emission can be obtained from the first organic compoundand the third organic compound. Since the light-emitting element 106 isprovided with the third layer 104, the degree of deterioration withdriving time can be improved.

The reason why the degree of deterioration is improved is considered asfollows: in the light-emitting element 115, electrons which do notcontribute to recombination at the interface between the first layer 112and the second layer 113 penetrate the second layer 113 to reach thehole-transporting layer 114, and thus deterioration occurs, whereas inthe light-emitting element 106, the number of electrons reaching thehole-transporting layer 105 is decreased due to the provision of thethird layer 104.

Note that if the fifth organic compound contained in the third layer 104as a host material which disperses an emission center substance is amaterial having a hole-transporting property, the number of electronsreaching the hole-transporting layer 105 can be further reduced, whichis preferable. Note that the fourth organic compound and the fifthorganic compound may be formed of the same material. In this case, ahost material does not need to be exchanged in forming the second layer103 and the third layer 104, and thus the manufacturing process can besomewhat simplified. Note that in the case of such a structure, thesecond layer 103 and the third layer 104 are distinguished by the kindof an emission center substance (the third organic compound or the firstorganic compound) which is a dopant.

As a preferable material as the host material which disperses anemission center substance, a condensed polycyclic material such as acondensed polycyclic aromatic compound typified by an anthracenederivative is given. Such a material has a large band gap; thus,excitation energy is difficult to transfer from an emission centersubstance and decline in emission efficiency or deterioration of colorpurity is unlikely to be caused. Moreover, such a material has either anelectron-transporting property or a hole-transporting property dependingon a substituent, and can be applied to light-emitting elements withvarious structures. However, in some cases, since a skeleton itself ofthe condensed polycyclic material has an electron-transporting property,the condensed polycyclic material also has ability to transport certainamount of electrons even when it is made to have a highhole-transporting property by a substituent, and effects ofdeterioration due to penetration of the electrons are increaseddepending on conditions. In such a case, the use of the light-emittingelement 106 of this embodiment mode makes it possible to effectivelysuppress deterioration. Note that as the condensed polycyclic materialused as a host material, tricyclic, tetracyclic, pentacyclic, andhexacyclic condensed aromatic compounds are especially effective.

Substances which emit different colors from each other may be used asthe first organic compound and the third organic compound each of whichis an emission center substance. Accordingly, the light-emitting element106 can emit light in which these two lights overlap, and variousemission colors can be obtained. The use of the structure of thelight-emitting element 106 of this embodiment mode makes it possible toobtain a light-emitting element which emits light with a desired colorand whose degree of deterioration with driving time is improved.

As described above, in the light-emitting element 106 of this embodimentmode, a recombination region of electrons and holes is located at theinterface between the first layer 102 and the second layer 103; thus, insome cases, energy transfer from an organic compound which emits lightwith a shorter wavelength from an organic compound which emits lightwith a longer wavelength occurs. In such a case, light emission from theorganic compound which emits light with a longer wavelength isinevitably becomes higher, and it becomes difficult to have balancedepending on a combination of colors. Therefore, especially in thestructure in which a substance which emits light with a wavelengthshorter than that of light emitted from the third organic compound isused as the first organic compound, little light emission from the firstorganic compound can be obtained by recombination of the electronspenetrating the second layer 103 and holes in the third layer 104. Thus,it becomes easy to balance emission colors of the light-emittingelement. Accordingly, a light-emitting element which emits light with adesired color can be easily obtained.

Note that the above-described structure of the light-emitting element106 of this embodiment is very effective in obtaining white lightemission. When the structure of the light-emitting element 106 of thisembodiment mode is used, a white light-emitting element in which desiredwhite balance is realized and whose degree of deterioration with drivingtime is improved can be obtained. Moreover, in the case where astructure is employed in which in the light-emitting element 106, asubstance which emits light with a wavelength shorter than that of lightemitted from the third organic compound is used as the first organiccompound, a light-emitting element can be obtained more easily in whichdesired white balance is realized and whose degree of deterioration withdriving time is improved.

In the case where a white light-emitting element is manufactured usingthe structure of the light-emitting element 106 of this embodiment mode,as a combination of light emitted from the first organic compound andthe third organic compound, a combination of colors which are in arelationship of complementary colors, such as red and blue green; oryellow and blue is preferably used. In particular, a structure in whicha substance which emits light with a wavelength shorter than that oflight emitted from the third organic compound is used as the firstorganic compound, for example, a combination of a substance which emitslight of blue as the first organic compound and a substance which emitslight of yellow as the third organic compound, or a combination of asubstance which emits light of blue green as the first organic compoundand a substance which emits light of red as the third organic compound,is preferable because such a structure makes it easy to balance emissioncolors of the light-emitting element.

In the case where a white light-emitting element is manufactured usingthe structure of the light-emitting element 106 of this embodiment mode,as examples of the combination of light emitted from the first organiccompound and light emitted from the third organic compound, there are acombination of light whose peak wavelength ranges from 600 nm to 700 nmand light whose peak wavelength ranges from 480 nm to 520 nm, and acombination of light whose peak wavelength ranges from 540 nm to 600 nmand light whose peak wavelength ranges from 400 nm to 480 nm. Needlessto say, also in this case, the structure using a substance which emitslight with a wavelength shorter than that of light emitted from thethird organic compound is used as the first organic compound ispreferable because the structure makes it easy to balance emissioncolors of the light-emitting element.

Next, the light-emitting element described above will be described morespecifically with a manufacturing method thereof. Note that an elementstructure and a manufacturing method described here are just an example,and other known structures, materials, and manufacturing methods can beapplied without departing from the purpose of the present invention.

FIG. 1 is a schematic view showing an example of an element structure ofthe light-emitting element of the present invention. The light-emittingelement shown in FIG. 1 has a structure including a layer 107 containingan organic compound, between the second electrode 100 and the firstelectrode 101. The layer 107 containing the organic compound has atleast a light-emitting layer having a stacked structure in which thethird layer 104 containing the first organic compound which is anemission center substance and the fifth organic compound which is a hostmaterial; the second layer 103 containing the third organic compoundwhich is an emission center substance and the fourth organic compoundwhich is a host material; and the first layer 102 containing the firstorganic compound and the second organic compound which is a hostmaterial are stacked in this order from the first electrode 101 side(here, whether the third layer emits light or not is no object), and ahole-transporting layer 105 provided in contact with the third layer104. An electron-injecting layer, an electron-transporting layer, or thelike may be provided between the light-emitting layer and the secondelectrode 100 as appropriate, and a layer such as a hole-injecting layermay be provided between the hole-transporting layer 105 and the firstelectrode 101 as appropriate. One of the first electrode 101 and thesecond electrode 100 is an anode, and the other is a cathode. In thisembodiment mode, the case where the first electrode 101 is an anode andthe second electrode 100 is a cathode will be described. Note that theanode in the present invention means an electrode which injects holes toa layer containing a light-emitting material and the cathode means anelectrode which injects electrons to the layer containing thelight-emitting material.

First, the anode is formed over an insulating surface. For the anode,metal, an alloy, a conductive compound, a mixture thereof, or the likehaving a high work function (specifically, 4.0 eV or higher) ispreferably used. Specifically, for example, the anode is formed usingindium tin oxide (ITO), indium tin oxide containing silicon or siliconoxide, indium oxide containing zinc oxide (ZnO), indium oxide containingtungsten oxide and zinc oxide (IWZO), or the like. Such a conductivemetal oxide film is generally formed by sputtering; however, it may beformed by application of a sol-gel method or the like. For example,indium oxide containing zinc oxide (ZnO) can be formed by a sputteringmethod using a target in which 1 wt % to 20 wt % of zinc oxide is addedto indium oxide. In addition, indium oxide containing tungsten oxide andzinc oxide (IWZO) can be formed by a sputtering method using a target inwhich 0.5 wt % to 5 wt % of tungsten oxide and 0.1 wt % to 1 wt % ofzinc oxide are added to indium oxide. Moreover, gold (Au), platinum(Pt), nickel (Ni), tungsten (W), chromium (Cr), molybdenum (Mo), iron(Fe), cobalt (Co), copper (Cu), palladium (Pd), a nitride of a metalmaterial (e.g., titanium nitride), or the like can be used.

Subsequently, the layer containing the organic compound is formed. Forthe layer 107 containing the organic compound, either a low molecularmaterial or a high molecular material can be used. In addition, thematerial forming the layer 107 containing the organic compound is notlimited to a material containing only an organic compound material, andmay partially contain an inorganic compound. In addition, the layer 107containing the organic compound is generally formed of a combination offunctional layers as appropriate, such as a hole-injecting layer, ahole-transporting layer, a hole blocking layer, a light-emitting layer,an electron-transporting layer, and an electron-injecting layer. Thelayer 107 containing the organic compound may include a layer having twoor more functions of the above layers, or not all the above layers maybe formed. Needless to say, a layer having a function other than thefunctions of the above-described layers may be provided. In thisembodiment mode, description is made using a light-emitting element, asan example, in which a stacked layer including a hole-injecting layer, ahole-transporting layer, a light-emitting layer (stacked body includingthe third layer 104, the second layer 103, and the first layer 102); anelectron-transporting layer, and an electron-injecting layer in thisorder from the anode side is used as the layer 107 containing theorganic compound.

In the case of using a hole-injecting layer, metal oxide such asvanadium oxide, molybdenum oxide, ruthenium oxide, and aluminum oxide,and the like are given as a material which functions as thehole-injecting layer. Alternatively, a porphyrin-based compound iseffective among organic compounds, and phthalocyanine (H₂Pc), copperphthalocyanine (CuPc), or the like can be used. A high molecularcompound (e.g., an oligomer, a dendrimer, or a polymer) can be used aswell for the hole-injecting layer. For example, high molecular compoundssuch as poly(N-vinylcarbazole) (PVK), poly(4-vinyl triphenylamine)(PVTPA),poly[N-(4-{N′-[4-(4-diphenylamino)phenyl]phenyl-N-phenylamino}phenyl)methacrylamide](PTPDMA), and poly[N,N-bis(4-butylphenyl)-N,N-bis(phenyl)benzidine(Poly-TPD) are given. In addition, high molecular compounds mixed withacid such as poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonic acid)(PEDOT/PSS) and polyaniline/poly(styrenesulfonic acid) (PAni/PSS) can beused. The hole-injecting layer is formed in contact with the anode, andwith use of the hole-injecting layer, a carrier injection barrier isreduced and carriers are efficiently injected to the light-emittingelement, which results in reduction of driving voltage.

Alternatively, for the hole-injecting layer, a material in which anacceptor material is contained in a substance having a hole-transportingproperty (hereinafter, the material is referred to as a “compositematerial”) can be used. Note that, by use of the substance having a highhole-transporting property containing an acceptor substance, thesubstance can have an ohmic contact with an electrode and a materialused to form an electrode may be selected regardless of its workfunction. In other words, besides a material having a high workfunction, a material with a low work function can be used as the anode.As the acceptor material,7,7,8,8-tetracyano-2,3,5,6-tetrafluoroquinodimethane (F₄-TCNQ),chloranil, or the like can be given. In addition, a transition metaloxide can be given. In addition, oxide of metal that belongs to Group 4to Group 8 of the periodic table can be given. Specifically, vanadiumoxide, niobium oxide, tantalum oxide, chromium oxide, molybdenum oxide,tungsten oxide, manganese oxide, and rhenium oxide are preferablebecause of a high electron accepting property. Among these, molybdenumoxide is especially preferable because it is stable in air, itshygroscopic property is low, and it can be easily treated.

Note that, in this specification, the term “composition” means not onlya simple mixture of two materials but also a mixture of a plurality ofmaterials in a condition where an electric charge is given and receivedbetween the materials.

As a substance having a high hole-transporting property used for thecomposite material, various compounds such as an aromatic aminecompound, a carbazole derivative, aromatic hydrocarbon, and a highmolecular compound (such as oligomer, dendrimer, or polymer) can beused. A substance having a hole mobility of 10⁻⁶ cm²/Vs or higher ispreferably used as a substance having a high hole-transporting propertyused for the composite material. However, substances other than theabove-described substance can be used as long as they have ahole-transporting property which is higher than an electron-transportingproperty. An organic compound which can be used as a substance having ahigh hole-transporting property for the composite material will bespecifically given below.

For example, as the aromatic amine compound which can be used for thecomposite material, the following can be given:4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (NPB or α-NPD);N,N′-bis(4-methylphenyl)-N,N′-diphenyl-p-phenylenediamine (DTDPPA);4,4′-bis[N-(4-diphenylaminophenyl)-N-phenylamino]biphenyl (DPAB);N,N′-bis[4-[bis(3-methylphenyl)amino]phenyl]-N,N-diphenyl-[1,1′-biphenyl]-4,4′-diamine(DNTPD); 1,3,5-tris[N-(4-diphenylaminophenyl)-N-phenylamino]benzene(DPA3B); and the like.

As the carbazole derivative which can be used for the compositematerial, the following can be given specifically:3-[N-(9-phenylcarbazol-3-yl)-N-phenylamino]-9-phenylcarbazole (PCzPCA1);3,6-bis[N-(9-phenylcarbazol-3-yl)-N-phenylamino]-9-phenylcarbazole(PCzPCA2);3-[N-(1-naphthyl)-N-(9-phenylcarbazol-3-yl)amino]-9-phenylcarbazole(PCzPCN1); and the like.

Moreover, as the carbazole derivative which can be used for thecomposite material, 4,4′-di(N-carbazolyl)biphenyl (CBP);1,3,5-tris[4-(N-carbazolyl)phenyl]benzene (TCPB);9-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazole (CzPA);1,4-bis[4-(N-carbazolyl)phenyl]-2,3,5,6-tetraphenylbenzene; or the likecan be used.

As the aromatic hydrocarbon which can be used for the compositematerial, the following can be given for example:2-tert-butyl-9,10-di(2-naphthyl)anthracene (t-BuDNA);2-tert-butyl-9,10-di(1-naphthyl)anthracene,9,10-bis(3,5-diphenylphenyl)anthracene (DPPA);2-tert-butyl-9,10-bis(4-phenylphenyl)anthracene (t-BuDBA);9,10-di(2-naphthyl)anthracene (DNA); 9,10-diphenylanthracene (DPAnth);2-tert-butylanthracene (t-BuAnth);9,10-bis(4-methyl-1-naphthyl)anthracene (DMNA);9,10-bis[2-(1-naphthyl)phenyl]-2-tert-butyl-anthracene;9,10-bis[2-(1-naphthyl)phenyl]anthracene;2,3,6,7-tetramethyl-9,10-di(1-naphthyl)anthracene;2,3,6,7-tetramethyl-9,10-di(2-naphthyl)anthracene; 9,9′-bianthryl;10,10′-diphenyl-9,9′-bianthryl;10,10′-bis(2-phenylphenyl)-9,9′-bianthryl;10,10′-bis[(2,3,4,5,6-pentaphenyl)phenyl]-9,9′-bianthryl; anthracene;tetracene; rubrene; perylene; 2,5,8,11-tetra(tert-butyl)perylene; andthe like. Besides those, pentacene, coronene, or the like can also beused. As described above, the aromatic hydrocarbon which has a holemobility of 1×10⁻⁶ cm²/Vs or higher and which has 14 to 42 carbon atomsis particularly preferable.

The aromatic hydrocarbon which can be used for the composite materialmay have a vinyl skeleton. As the aromatic hydrocarbon having a vinylgroup, the following can be given as examples:4,4′-bis(2,2-diphenylvinyl)biphenyl (DPVBi);9,10-bis[4-(2,2-diphenylvinyl)phenyl]anthracene (DPVPA); and the like.

Alternatively, a composite material which is formed using theabove-described high molecular compound such as PVK, PVTPA, PTPDMA, orpoly-TPD and the above-described substance with an acceptor property maybe used as the hole-injecting layer.

When the composite material described above is used for thehole-injecting layer, various kinds of metal, alloys, electricallyconductive compounds or mixture thereof can be used for the anode,regardless of the work function. Therefore, for example, aluminum (Al),silver (Ag), an aluminum alloy (e.g., AlSi), or the like can be used forthe anode, in addition to the above-described materials. In addition, anelement belonging to Group 1 or Group 2 in the periodic table, which isa low work function material, that is, alkali metal such as lithium (Li)or cesium (Cs), alkaline earth metal such as magnesium (Mg), calcium(Ca), or strontium (Sr), an alloy containing these metals (e.g., MgAg orAlLi), rare earth metal such as europium (Eu) or ytterbium (Yb), analloy containing such rare earth metal, or the like can be used. A filmof alkali metal, alkaline earth metal, or an alloy containing thesemetals can be formed by a vacuum evaporation method. In addition, a filmof an alloy containing alkali metal or alkaline earth metal can beformed by sputtering. Moreover, silver paste or the like can be formedby an ink-jet method.

For the hole-transporting layer, appropriate materials such asN,N′-bis[N-(spiro-9,9′-bifluoren-2-yl)-N-phenylamino]biphenyl (BSPB);4,4′-bis[N-(l-naphthyl)-N-phenylamino]biphenyl (NPB or α-NPD);N,N′-bis(3-methylphenyl)-N,N′-dipheny-[1,1′-biphenyl]-4,4′-diamine(TPD); 4,4′,4″-tris(N,N-diphenylamino)triphenylamine (TDATA);4,4′,4″-tris[N-(3-methylphenyl)-N-phenylamino]triphenylamine (MTDATA);N,N′-bis[4-[bis(3-methylphenyl)amino]phenyl]-N,N′-diphenyl-[1,1′-biphenyl]-4,4′-diamine (DNTPD); 1,3,5-tris[N,N-di(m-tolyl)amino]benzene (m-MTDAB);4,4′,4″-tris(N-carbazolyl)triphenylamine (TCTA); phthalocyanine (H₂Pc);copper phthalocyanine (CuPc); or vanadyl phthalocyanine (VOPc) can beused. Although a substance having a hole mobility of 10⁻⁶ cm²/Vs orhigher is preferably used for the hole-transporting layer, any substancecan be used for the hole-transporting layer as long as thehole-transporting property is higher than an electron-transportingproperty. Moreover, the hole-transporting layer is not limited to asingle-layer structure, and may be formed as a multilayer structure inwhich two or more layers formed of substances which satisfy theabove-described conditions are mixed. The hole-transporting layer can beformed by a vacuum evaporation method, or the like.

As the hole-transporting layer, a high molecular compound such as PVK,PVTPA, PTPDMA, or Poly-TPD can be used. In this case, a solution processsuch as an ink-jet method or a spin coating method can be used.

Note that the hole-transporting layer which is in contact with thelight-emitting layer is preferably formed of a substance having anexcitation energy higher than that of the first organic compound whichis an emission center substance of the third layer 104. Such a structuremakes it possible to suppress energy transfer from the light-emittinglayer to the hole-transporting layer and realize high emissionefficiency.

In the light-emitting layer, the third layer 104, the second layer 103,and the first layer 102 are stacked from the first electrode 101 side.The first organic compound which serves as an emission center and thesecond organic compound as a host material which disperses the firstorganic compound are contained in the first layer 102. The third organiccompound which serves as an emission center and the fourth organiccompound as a host material which disperses the third organic compoundare contained in the second layer 103. The first organic compound whichserves as an emission center and the fifth organic compound as a hostmaterial which disperses the first organic compound are contained in thethird layer 104. Here, the first organic compound in the first layer 102and the first organic compound in the third layer 104 are the samesubstance. The second organic compound is formed of a material having anelectron-transporting property. The fourth organic compound and thefifth organic compound are formed of a material having ahole-transporting property. Note that, since a host material has afunction of dispersing a substance which serves as an emission center,the amount of the host material in each layer is larger than that of thesubstance which serves as an emission center. Moreover, the proportionof the substance which serves as an emission center in each layer may beset to greater than or equal to 0.1 wt % and less than 50 wt %. Thelight-emitting layer can be formed by a vacuum evaporation method, andit can be formed by a co-evaporation method in which different materialsare evaporated at the same time.

The first organic compound and the third organic compound are each asubstance which serves as an emission center, and substances which emitlight with different wavelengths from each other are selected for thefirst organic compound and the third organic compound. Although examplesof the substance which serves as an emission center are given below,needless to say, the substance which serves as an emission center is notlimited to the substances. As examples of substances which exhibits blueemission (emission wavelength: 400 nm to 480 nm), there areN,N′-bis[4-(9H-carbazol-9-yl)phenyl]-N,N′-diphenylstilbene-4,4′diamine(YGA2S); 4-(9H-carbazol-9-yl)-4′-(10-phenyl-9-anthryl)triphenylamine(YGAPA);4-(9H-carbazol-9-yl)-4′-(10-phenyl-9-yl)-4′-(9,10-diphenyl-2-anthryl)triphenylamine(2YGAPPA);N,9-diphenyl-N-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazol-3-amine(PCAPA);4-(10-phenyl-9-anthryl)-4′-(9-phenyl-9H-carbazol-3-yl)triphenylamine(PCBAPA); perylene; 2,5,8,11-tetra(tert-butyl)perylene (TBP); and thelike. In addition, materials which emit phosphorescence, such asbis[2-(4′,6′-difluorophenyl)pyridinato-N,C²′]iridium(III)tetrakis(1-pyrazolyl)borate(FIr6) andbis[2-(4′6′-difluorophenyl)pyridinato-N,C²′]iridium(III)picolinate(FIrpic) can be used. As examples of substances which exhibit blue greenlight emission (emission wavelength: 480 nm to 520 nm), there areN,N″-(2-tert-butylanthracene-9,10-diyldi-4,1-phenylene)bis[N,N′,N′-triphenyl-1,4-phenylenediamine](DPABPA);N,9-diphenyl-N-[4-(9,10-diphenyl-2-anthryl)phenyl]-9H-carbazole-3-amine(2PCAPPA);N-[4-(9,10-diphenyl-2-anthryl)phenyl]-N,N′,N′-triphenyl-1,4-phenyldiamine(2DPAPPA); N, N, N′, N′, N″, N″, N′″,N′″-octaphenyldibenzo[g,p]chrysene-2,7,10,15-tetramine (DBC1); coumarin30; and the like. In addition, materials which emit phosphorescence,such asbis[2-(3′,5′bistrifluoromethylphenyl)pyridinato-N,C²′]iridium(III)picolinate(Ir(CF₃ppy)₂(pic)); andbis[2-(4′,6′-difluorophenyl)pyridinato-N,C²′]iridium(III)acetylacetonate(FIr(acac)); can be used. As examples of substances which exhibit yellowlight emission (emission wavelength: 540 nm to 600 nm), there arerubrene; 5,12-bis(1,1′-biphenyl-4-yl)-6,11-diphenyltetracene (BPT);2-{2-[4-(dimethylamino)phenyl]ethenyl}-6-methyl-4H-pyran-4-ylidene)propanedinitrile(DCM1);2-{2-methyl-6-[2-(2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinolizin-9-yl)ethenyl]-4H-pyran-4-ylidene}propanedinitrile (DCM2); and the like. In addition,materials which emit phosphorescence, such asbis(benzo[h]quinolinato)iridium(III)acetylacetonate (Ir(bzq)₂(acac));bis(2,4-diphenyl-1,3-oxazolato-N,C²′)iridium(III)acetylacetonate(Ir(dpo)₂(acac));bis[2-(4′-perfluorophenylphenyl)pyridinato]iridium(III) acetylacetonate(Ir(p-PF-ph)₂(acac)); andbis(2-phenylbenzothiazolato-N,C²′)iridium(III)acetylacetonate(Ir(bt)₂(acac)) can be used. As examples of substances which exhibit redlight emission (emission wavelength: 600 nm to 700 nm), there areN,N,N′,N′-tetrakis(4-methylphenyl)tetracene-5,11-diamine (p-mPhTD);7,13-diphenyl-N,N,N′,N′-tetrakis(4-methylphenyl)acenaphtho[1,2-a]fluoranthene-3,10-diamine (p-mPhAFD);{2-isopropyl-6-[2-(1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinolizin-9-yl)ethenyl]-4H-pyran-4-ylidene}propanedinitrile(DCJTI);{2-tert-butyl-6-[2-(1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinolizin-9-yl)ethenyl]-4H-pyran-4-ylidene}propanedinitrile(DCJTB); 4-(dicyanomethylene)-2,6-bis[p-(dimethylamino)styryl]-4H-pyran(BisDCM);{2,6-bis[2-(8-methoxy-1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinolizin-9-yl)ethenyl]-4H-pyran-4-ylidene}propanedinitrile(BisDCJTM); and the like. In addition, materials which emitphosphorescence, such asbis[2-(2′-benzo[4,5-a]thienyl)pyridinato-N,C³′]Iridium(III)acetylacetonate(Ir(btp)₂(acac));bis(1-phenylisoquinolinato-N,C²′)iridium(III)acetylacetonate(Ir(piq)₂(acac));(acetylacetonato)bis[2,3-bis(4-fluorophenyl)quinoxalinato]iridium(III)(Ir(Fdpq)₂(acac));2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphyrinplatinum(II) (PtOEP); andtris(1,3-diphenyl-1,3-propanedionato) (monophenanthroline)europium(III)(Eu(DBM)₃(Phen)) can be used. Note that, although materials which emitlight with a wavelength of 520 nm to 540 nm are not given, it isneedless to say that light-emitting materials (including materials whichemit phosphorescence in its category) with a wavelength of this rangecan be used. Substances which have different emission wavelengths can beselected from these substances to be used so that a desired emissioncolor can be obtained from the light-emitting element. As examples ofthe combinations, when 2YGAPPA is used as the first organic compound andrubrene is used as the third organic compound, white color can beobtained; when 2PCAPPA is used as the first organic compound and BisDCMis used as the third organic compound, white color can be obtained; andwhen 2YGAPPA is used as the first organic compound and BisDCM is used asthe third organic compound, an intermediate color such as purple can beobtained.

Since the recombination region of electrons and holes is located nearthe interface between the first layer 102 and the second layer 103,energy transfer from an organic compound which emits light with ashorter wavelength to an organic compound which emits light with alonger wavelength occurs in some cases. In such a case, emission fromthe organic compound which emits light with a longer wavelengthinevitably becomes higher, and it is difficult to have balance dependingon a combination of colors. At this time, if the substance which emitslight with a shorter wavelength is used as the first organic compoundand the substance which emits light with a longer wavelength is used asthe third organic compound, little light emission from the first organiccompound can be obtained by recombination of the electrons penetratingthe second layer 103 and holes in the third layer 104. Thus, it becomeseasy to balance emission colors of the light-emitting element.Accordingly, a light-emitting element which exhibits a desired emissioncolor and whose degree of deterioration with driving time is improvedcan be easily obtained. Such a structure is effective especially inadjusting white balance of a white light-emitting element.

As the second organic compound, the fourth organic compound, and thefifth organic compound which are used as a host material which dispersesthe first organic compound or the third organic compound, the followingcan be given: metal complexes such as tris(8-quinolinolato)aluminum(Alq), tris(4-methyl-8-quinolinolato)aluminum (Almq₃),bis(10-hydroxybenzo[h]quinolinato)beryllium (BeBq₂), orbis(2-methyl-8-quinolinolato)(4-phenylphenolato)aluminum (BAlq),bis(8-quinolinolato)zinc(II) (Znq),bis[2-(2-benzoxazolyl)phenolato]zinc(II) (ZnPBO), andbis[2-(2-hydroxyphenyl)benzothiazolato]zinc(II) (ZnBTZ); heterocycliccompounds such as2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (PBD),1,3-bis[5-(p-tert-butylphenyl)-1,3,4-oxadiazol-2-yl]benzene (OXD-7),3-(4-biphenylyl)-4-phenyl-5-(4-tert-butylphenyl)-1,2,4-triazole (TAZ),2,2′,2″-(1,3,5-benzenetriyl)tris(1-phenyl-1H-benzimidazole) (TPBI),bathophenanthroline (BPhen), and bathocuproine (BCP), and9-[4-(5-phenyl-1,3,4-oxadiazol-2-yl)phenyl]carbazole (CO11); andaromatic amine compounds such as NPB (or α-NPD), TPD, and BSPB. Inaddition, condensed polycyclic aromatic compounds such as anthracenederivatives, phenanthrene derivatives, pyrene derivatives, chrysenederivatives, and dibenzo[g,p]chrysene derivatives are given. Thefollowing is specifically given as the condensed polycyclic aromaticcompound: 9,10-diphenylanthracene (DPAnth);N,N-diphenyl-9-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazol-3-amine(CzA1PA); 4-(10-phenyl-9-anthryl)triphenylamine (DPhPA);4-(9H-carbazol-9-yl)-4′-(10-phenyl-9-anthryl)triphenylamine (YGAPA);N,9-diphenyl-N-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazol-3-amine(PCAPA);N,9-diphenyl-N-{4-[4-(10-phenyl-9-anthryl)phenyl]phenyl}-9H-carbazol-3-amine(PCAPBA); N-9-diphenyl-N-(9,10-diphenyl-2-anthryl)-9H-carbazol-3-amine(2PCAPA);9-phenyl-9′-[4-(10-phenyl-9-anthryl)phenyl]-3,3′-bi(9H-carbazole)(PCCPA);4-(10-phenyl-9-anthryl)4′-(9-phenyl-9H-carbazol-3-yl)triphenylamine(PCBAPA); 6,12-dimethoxy-5,11-diphenylchrysene,N,N,N′,N′,N″,N″,N′″,N′″-octaphenyldibenzo[g,p]chrysene-2,7,10,15-tetramine(DBC1); 9-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazole (CzPA);3,6-diphenyl-9-[4-(10-phenyl-9-antryl)phenyl]-9H-carbazole (DPCzPA),9,10-bis(3,5-diphenylphenyl)anthracene (DPPA),9,10-di(2-naphthyl)anthracene (DNA),2-tert-butyl-9,10-di(2-naphthyl)anthracene (t-BuDNA), 9,9′-bianthryl(BANT), 9,9′-(stilbene-3,3′-diyl)diphenanthrene (DPNS),9,9′-(stilbene-4,4′-diyl)diphenanthrene (DPNS2),3,3′,3″-(benzene-1,3,5-triyl)tripyrene (TPB3) and the like. A substancehaving an energy gap which is larger than that of an emission centersubstance dispersed by each substance may be selected from thesesubstances and known substances. Moreover, in the case where an emissioncenter substance emits phosphorescence, a substance having a tripletenergy (energy difference between a ground state and a tripletexcitation state) which is higher than that of the emission centersubstance may be selected as a host material.

Note that the fourth organic compound and the fifth organic compound arepreferably a material having a hole-transporting property, and thesecond organic compound is preferably a material having anelectron-transporting property. As the material having ahole-transporting property, the following can be given: theabove-described aromatic amine compounds and condensed polycyclicaromatic compounds such as DPAnth, CzA1PA, DPhPA, YGAPA, PCAPA, PCAPBA,2PCAPA, and DBC1. As the materials having an electron-transportingproperty, the following can be given: the above-described heterocycliccompounds and condensed polycyclic aromatic compounds such as CzPA,DPCzPA, DPPA, DNA, t-BuDNA, BANT, DPNS, DPNS2, and TPB3.

Among the above-described substances, the condensed polycyclic compoundsparticularly have a large band gap and can be preferably used as a hostmaterial for dispersing an emission center substance; however, even ifthe condensed polycyclic aromatic compounds are used as the materialhaving a hole-transporting property, it has ability to transport acertain amount of electrons and deterioration due to penetration ofelectrons to the hole-transporting layer is increased in some cases.Therefore, in the case where DPAnth, CzA1PA, DPhPA, YGAPA, PCAPA,PCAPBA, 2PCAPA, DBC1, PCBAPA, PCCPA, or the like which is the condensedpolycyclic aromatic compound having a hole-transporting property is usedas the fourth organic compound, deterioration can be suppressed veryeffectively by use of the structure of the light-emitting element ofthis embodiment mode.

In the case of using an electron-transporting layer, it is providedbetween a light-emitting layer and an electron-injecting layer. Assuitable materials, metal complexes having a quinoline skeleton or abenzoquinoline skeleton, such as tris(8-quinolinolato)aluminum (Alq),tris(4-methyl-8-quinolinolato)aluminum (Almq₃),bis(10-hydroxybenzo[h]-quinolinato)beryllium (BeBq₂), andbis(2-methyl-8-quinolinolato)(4-phenylphenolato)aluminum (BAlq) can beused. Besides these materials, metal complexes having an oxazole ligandor a thiazole ligand, such as bis[2-(2-hydroxyphenyl)benzoxazolato]zinc(Zn(BOX)₂) and bis[2-(2-hydroxyphenyl)benzothiazolato]zinc (Zn(BTZ)₂),and the like can also be used. Furthermore, beside the metal complexes,2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (PBD),1,3-bis[5-(p-tert-butylphenyl)-1,3,4-oxadiazol-2-yl]benzene (OXD-7),bathophenanthroline (BPhen), bathocuproine (BCP), and the like can alsobe used. Although a substance having an electron mobility of 10⁻⁶ cm²/Vsor higher is preferably used for the electron-transporting layer, anysubstance can be used for the electron-transporting layer as long as ithas an electron-transporting property higher than a hole-transportingproperty. Moreover, the electron-transporting layer is not limited to asingle-layer structure, and may be formed as a multilayer structure inwhich two or more layers formed of substances which satisfy theabove-described conditions are mixed. The electron-transporting layercan be formed by a vacuum evaporation method, or the like.

Alternatively, a high molecular compound can be used for theelectron-transporting layer. For example,poly[(9,9-dihexylfluorene-2,7-diyl)-co-(pyridin-3,5-diyl)] (PF-Py),poly[(9,9-dioctyllfluorene-2,7-diyl)-co-(2,2′-pyridin-6,6′-diyl)](PF-BPy), or the like can be used. In this case, a solution process suchas an ink-jet method or a spin coating method can be used.

Note that for the electron-transporting layer which is in contact withthe light-emitting layer, a substance having excitation energy higherthan excitation energy of the first organic compound which is anemission center substance of the third layer 104 is preferably used.Such a structure makes it possible to suppress energy transfer from thelight-emitting layer to the electron-transporting layer and realize highemission efficiency.

In the case of using an electron-injecting layer, there is no particularlimitation on an electron-injecting material used for forming theelectron-injecting layer. Specifically, an alkali metal compound or analkaline earth metal compound such as calcium fluoride, lithiumfluoride, lithium oxide, or lithium chloride, or the like is preferable.Alternatively, a layer in which an electron-transporting material suchas tris(8-quinolinolato)aluminum (Alq) or bathocuproine (BCP) iscombined with alkali metal or alkaline earth metal such as lithium ormagnesium can also be used. The electron-injecting layer is formed incontact with a cathode, and a carrier injection barrier is reduced byuse of the electron-injecting layer, so that carriers are efficientlyinjected into the light-emitting element, which results in reduction ofdriving voltage. It is more preferable that the electron-injecting layerbe formed using the layer in which a substance having anelectron-transporting property is combined with alkali metal or alkalineearth metal, because electron injection from the cathode efficientlyproceeds. The electron-injecting layer can be formed by a vacuumevaporation method or the like.

Note that the layer 107 containing the organic compound can be formed byeither a wet process or a dry process, such as an evaporation method, anink-jet method, a spin coating method, or a dip coating method, as wellas the above-described formation method.

Moreover, when the electron-injecting layer is provided between thecathode and the electron-transporting layer, any of a variety ofconductive materials such as Al, Ag, ITO, and indium tin oxidecontaining silicon or silicon oxide can be used regardless of its workfunction.

After that, a cathode is formed, so that the light-emitting element iscompleted. The cathode can be formed using metal, an alloy, a conductivecompound, and a mixture thereof each having a low work function(specifically, 3.8 eV or lower). Specifically, metal belonging to Group1 or 2 of the periodic table, that is, alkali metal such as lithium (Li)or cesium (Cs); alkaline earth metal such as magnesium (Mg), calcium(Ca), or strontium (Sr); or an alloy containing such metal (e.g., MgAgor AlLi); rare earth metal such as europium (Er) or ytterbium (Yb), analloy containing these, or the like can be given. A film made of alkalimetal, alkaline earth metal, or an alloy of them can be formed by avacuum evaporation method. Further, a film made of an alloy of alkalimetal or alkaline earth metal can be formed by a sputtering method. Itis also possible to deposit silver paste or the like by an ink-jetmethod or the like.

Note that a conductive composition containing a conductive high molecule(also referred to as a “conductive polymer”) can be used for the anodeand the cathode. When a thin film of a conductive composition is formedas the anode or the cathode, the thin film preferably has sheetresistance of less than or equal to 10000 Ω/square and lighttransmittance of greater than or equal to 70% at a wavelength of 550 nm.Note that resistance of a conductive high molecule which is contained inthe thin film is preferably less than or equal to 0.1 Ω·cm.

As a conductive high molecule, a so-called at electron conjugated highmolecule can be used. For example, polyaniline and/or a derivativethereof, polypyrrole and/or a derivative thereof, polythiophene and/or aderivative thereof, and a copolymer of two or more kinds of thosematerials can be given.

Specific examples of a conjugated conductive high molecule are givenbelow: polypyrrole, poly(3-methylpyrrole), poly(3-butylpyrrole),poly(3-octylpyrrole), poly(3-decylpyrrole), poly(3,4-dimethylpyrrole),poly(3,4-dibutylpyrrole), poly(3-hydroxypyrrole),poly(3-methyl-4-hydroxypyrrole), poly(3-methoxypyrrole),poly(3-ethoxypyrrole), poly(3-octoxypyrrole), poly(3-carboxylpyrrole),poly(3-methyl-4-carboxylpyrrole), polyN-methylpyrrole, polythiophene,poly(3-methylthiophene), poly(3-butylthiophene), poly(3-octylthiophene),poly(3-decylthiophene), poly(3-dodecylthiophene),poly(3-methoxythiophene), poly(3-ethoxythiophene),poly(3-octoxythiophene), poly(3-carboxylthiophene),poly(3-methyl-4-carboxylthiophene), poly(3,4-ethylenedioxythiophene),polyaniline, poly(2-methylaniline), poly(2-octylaniline)poly(2-isobutylaniline), poly(3-isobutylaniline), poly(2-anilinesulfonicacid), or poly(3-anilinesulfonic acid).

One of the above-described conductive high molecular compounds can beused alone for the anode or the cathode, or an organic resin is added tosuch a conductive high molecular compound in order to adjust filmcharacteristics such that it can be used as a conductive composition.

As for an organic resin, a thermosetting resin, a thermoplastic resin,or a photocurable resin may be used as long as such a resin iscompatible to a conductive high molecule or a resin can be mixed withand dispersed into a conductive high molecule. For example, apolyester-based resin such as polyethylene terephthalate, polybutyleneterephthalate, or polyethylene naphthalate; a polyimide-based resin suchas polyimide or polyimide amide; a polyamide resin such as polyamide 6,polyamide 6,6, polyamide 12, or polyamide 11; a fluorine resin such aspolyvinylidene fluoride, polyvinyl fluoride, polytetrafluoroethylene,ethylenetetrafluoroethylene copolymer, or polychlorotrifluoroethylene; avinyl resin such as polyvinyl alcohol, polyvinyl ether, polyvinylbutyral, polyvinyl acetate, or polyvinyl chloride; an epoxy resin; axylene resin; an aramid resin; a polyurethane-based resin; apolyurea-based resin, a melamine resin; a phenol-based resin; polyether;an acrylic-based resin, or a copolymer of any of those resins can begiven.

Furthermore, the conductive high molecule or conductive composition maybe doped with an acceptor dopant or a donor dopant so thatoxidation-reduction potential of a conjugated electron in the conductivehigh-molecule or the conductive composition may be changed in order toadjust conductivity of the conductive high molecule or conductivecomposition.

As the acceptor dopant, a halogen compound, Lewis acid, proton acid, anorganic cyano compound, an organometallic compound, or the like can beused. As examples of the halogen compound, chlorine, bromine, iodine,iodine chloride, iodine bromide, iodine fluoride, and the like can begiven. As examples of the Lewis acid, phosphorus pentafluoride, arsenicpentafluoride, antimony pentafluoride, boron trifluoride, borontrichloride, boron tribromide, and the like can be given. As examples ofthe proton acid, inorganic acid such as hydrochloric acid, sulfuricacid, nitric acid, phosphoric acid, fluoroboric acid, hydrofluoric acid,and perchloric acid, and organic acid such as organic carboxylic acidand organic sulfonic acid can be given. As the organic carboxylic acidand the organic sulfonic acid, carboxylic acid compounds or sufonic acidcompounds can be used. As the organic cyano compound, a compound inwhich two or more cyano groups are included in a conjugated bond can beused. As an organic cyano compound, a compound having two or more cyanogroups in conjugated bonding, for example, tetracyanoethylene,tetracyanoethylene oxide, tetracyanobenzene, tetracyanoquinodimethane,and tetracyanoazanaphthalene are given.

As the donor dopant, alkali metal, alkaline earth metal, a quaternaryamine compound, and the like can be given.

A thin film used for the anode or the cathode can be formed by a wetprocess using a solution in which the conductive high molecule or theconductive composition is dissolved in water or an organic solvent(e.g., an alcohol solvent, a ketone solvent, an ester solvent, ahydrocarbon solvent, or an aromatic solvent):

The solvent for dissolving the conductive high molecule or theconductive composition is not particularly limited. A solvent whichdissolves the above-described conductive high molecule and polymer resincompound may be used. For example, the conductive composition may bedissolved in a single solvent or a mixed solvent of the following:water, methanol, ethanol, propylene carbonate, N-methylpyrrolidone,dimethylformamide, dimethylacetamide, cyclohexanone, acetone,methyletylketone, methylisobutylketone, toluene, and/or the like.

A film of the conductive composition can be formed by a wet process suchas an application method, a coating method, a droplet discharge method(also referred to as “an ink-jet method”), or a printing method afterthe conductive composition is dissolved in a solvent. The solvent may bedried with thermal treatment or may be dried under reduced pressure. Inthe case where the organic resin is a thermosetting resin, heattreatment may be further performed. In the case where the organic resinis a photocurable resin, light irradiation treatment may be performed.

Note that by change of types of the second electrode 100 and the firstelectrode 101, the light-emitting element of this embodiment mode hasvariations. When the second electrode 100 has a light-transmittingproperty, light is emitted from the second electrode 100 side, whereaswhen the second electrode 100 has a light-shielding property(reflectivity, in particular) and the first electrode 101 has alight-transmitting property, light is emitted from the first electrode101 side. Furthermore, when both the second electrode 100 and the firstelectrode 101 have a light-transmitting property, light can be emittedfrom both the first electrode side and the second electrode side.

Embodiment Mode 2

In this embodiment mode, an example of a light-emitting devicemanufactured using the light-emitting element described in EmbodimentMode 1 will be described. Note that the light-emitting device of thepresent invention is not limited to a light-emitting device having astructure described below, and it includes, in its category, all modesin each of which a display portion (e.g., a pixel portion 602 in thisembodiment mode) includes the light-emitting element described inEmbodiment Mode 1.

An example of a light-emitting device manufactured using thelight-emitting element described in Embodiment Mode 1 will be describedwith reference to FIGS. 3A and 3B. FIG. 3A is a top view of thelight-emitting device, and FIG. 3B is a cross-sectional view taken alongA-A′ and B-B′ in FIG. 3A. This light-emitting device includes a drivercircuit portion (a source side driver circuit) 601, a pixel portion 602,and a driver circuit portion (a gate side driver circuit) 603 in orderto control the light emission of the light-emitting element. Also, areference numeral 604 represents a sealing substrate, a referencenumeral 605 represents a sealant, and the inside surrounded by thesealant 605 is a space 607.

A lead wiring 608 is a wiring for transmitting a signal to be inputtedto the source side driver circuit 601 and the gate side driver circuit603, and this wiring 608 receives a video signal, a clock signal, astart signal, a reset signal, and the like from a flexible printedcircuit (FPC) 609 that is an external input terminal. Although only theFPC is illustrated here, the FPC may be provided with a printed wiringboard (PWB). The light-emitting device in this specification includesnot only the light-emitting device itself but also the light-emittingdevice to which an FPC or a PWB is attached.

Next, a cross-sectional structure will be explained with reference toFIG. 3B. The driver circuit portion and the pixel portion are formedover an element substrate 610. Here, the source driver circuit 601 whichis the driver circuit portion and one pixel in the pixel portion 602 areshown.

A CMOS circuit in which an n-channel TFT 623 and a p-channel TFT 624 arecombined formed for the source side driver circuit 601. The drivercircuit may be formed by various CMOS circuits, PMOS circuits, or NMOScircuits. Although a driver integration type in which a driver circuitis formed over the same substrate is described in this embodiment mode,it is not necessarily formed over the same substrate and a drivercircuit can be formed not over a substrate but outside a substrate.

The pixel portion 602 has a plurality of pixels, each of which includesa switching TFT 611, a current control TFT 612, a first electrode 613which is electrically connected to a drain of the current control TFT612, and a light-emitting element including the first electrode 613, alayer 616 containing an organic compound, and a second electrode 617.Note that an insulator 614 is formed so as to cover an end portion ofthe first electrode 613. In this embodiment mode, the insulator 614 isformed using a positive photosensitive acrylic resin film.

In order to obtain favorable coverage, the insulator 614 is formed tohave a curved surface with curvature at an upper end portion or a lowerend portion thereof. For example, in the case of using a positivephotosensitive acrylic resin as a material for the insulator 614, theinsulator 614 is preferably formed so as to have a curved surface with acurvature radius (0.2 μm to 3 μm) only at the upper end portion thereof.Either a negative type which becomes insoluble in an etchant by lightirradiation or a positive type which becomes soluble in an etchant bylight irradiation can be used as the insulator 614.

The layer 616 containing the organic compound and the second electrode617 are formed over the first electrode 613, so that a light-emittingelement is formed. As a material used for the first electrode 613 whichserves as an anode, metal, an alloy, a conductive compound, and amixture thereof each having a high work function (specifically, 4.0 eVor higher) is preferably used. Sequentially, a single layer of indiumtin oxide (ITO), indium tin oxide containing silicon or silicon oxide,indium oxide containing zinc oxide (ZnO), indium oxide containingtungsten oxide and zinc oxide (IWZO), gold (Au), platinum (Pt), nickel(Ni), tungsten (W), chromium (Cr), molybdenum (Mo), iron (Fe), cobalt(Co), copper (Cu), palladium (Pd), or nitride of a metal material (e.g.,titanium nitride), can be used. Moreover, a stacked-layer structureincluding a film containing titanium nitride and a film containingaluminum as its main component; a three-layer structure including atitanium nitride film, a film containing aluminum as its main component,and a titanium nitride film; or the like can be used. When thestacked-layer structure is used, low wiring resistance, favorable ohmiccontact, and a function as an anode are achieved.

The layer 616 containing the organic compound has a similar structure tothe layer 107 containing the organic compound described in EmbodimentMode 1. Either low molecular compounds or high molecular compounds(including oligomers and dendrimers) may be employed as the materialused for the layer 616 containing the organic compound. Moreover, notonly organic compounds but also inorganic compounds can be partiallyused for the material for forming the layer 616 containing the organiccompound. In addition, the layer 616 containing the organic compound isformed by various methods such as an evaporation method using anevaporation mask, an ink-jet method, and a spin coating method.

As a material used for the second electrode 617, which is formed overthe layer 616 containing the organic compound and serves as a cathode, amaterial having a low work function (Al, Mg, Li, Ca, or an alloy or acompound thereof, such as MgAg, MgIn, AlLi, LiF, or CaF₂) is preferablyused. In the case where light generated in the layer 616 containing theorganic compound is transmitted through the second electrode 617,stacked layers of a metal thin film with reduced thickness and atransparent conductive film (ITO, indium oxide containing 2 wt % to 20wt % of zinc oxide, indium tin oxide containing silicon or siliconoxide, zinc oxide (ZnO); or the like) are preferably used as the secondelectrode 617.

Here, the light-emitting element includes the first electrode 613, thelayer 616 containing the organic compound, and the second electrode 617.The specific structures and materials of the light-emitting element havebeen described in Embodiment Mode 1, and the repeated description isomitted. The description in Embodiment Mode 1 is to be referred to. Notethat the first electrode 613, the layer 616 containing the organiccompound, and the second electrode 617 in this embodiment modecorrespond to the first electrode 101, the layer 107 containing theorganic compound, and the second electrode 100 in Embodiment Mode 1,respectively.

The element substrate 610 in which TFTs for the driver circuit and thepixel portion as described above and the light-emitting element areformed is attached to the sealing substrate 604 with a sealant 605, sothat a light-emitting device can be provided, in which thelight-emitting element 106 described in Embodiment Mode 1 is provided inthe space 607 surrounded by the element substrate 610, the sealingsubstrate 604, and the sealant 605. Note that the space 607 is filledwith a filler. There are cases where the space 607 may be filled with aninert gas (such as nitrogen or argon), or where the space 607 may befilled with the sealant 605.

Note that an epoxy-based resin is preferably used as the sealant 605. Itis preferable that the material allow as little moisture and oxygen aspossible to penetrate therethrough. As the sealing substrate 604, aplastic substrate formed of FRP (fiberglass-reinforced plastics), PVF(polyvinyl fluoride), a polyester film, polyester, acrylic, or the likecan be used besides a glass substrate or a quartz substrate.

As described above, a light-emitting device of the present inventionmanufactured using the light-emitting element described in EmbodimentMode 1 can be obtained

The light-emitting device of the present invention uses thelight-emitting element described in Embodiment Mode 1 whose degree ofdeterioration with accumulation of driving time is reduced, and thus ahighly reliable light-emitting device can be obtained. Moreover, thelight-emitting element easily realizes an emission color which isintended by a designer, and thus a display device with excellent displayquality can be obtained.

Moreover, the light-emitting element described in Embodiment Mode 1 hasa structure which is preferable as a white light-emitting element; thus,it can be preferably used for lighting.

In this embodiment mode, the active light-emitting device in which thedriving of the light-emitting element is controlled by a transistor hasbeen described. However, a passive light-emitting device may be adopted.FIGS. 4A and 4B are views of a passive matrix type light-emitting deviceformed according to the present invention. FIG. 4A is a perspective viewof the light-emitting device, and FIG. 4B is a cross-sectional viewtaken along a line X-Y in FIG. 4A. In FIGS. 4A and 4B, over a substrate951, a layer 955 containing an organic compound is provided between anelectrode 952 and an electrode 956. An end of the electrode 952 iscovered with an insulating layer 953. Sidewalls of the partition layer954 are slanted so that a distance between one of the sidewalls and theother becomes narrower toward a substrate surface. In other words, across section of the partition layer 954 in the direction of a narrowside is trapezoidal, and a base (a side which is in contact with theinsulating layer 953) is shorter than an upper side (a side which is incontact with the insulating layer 953). The partition layer 954 providedin this manner can prevent the light-emitting element from beingdefective due to static electricity or the like. Also in a passivematrix light-emitting device, the light-emitting element described inEmbodiment Mode 1 is used, whose degree of deterioration withaccumulation of driving time is reduced; thus, a highly reliablelight-emitting device can be obtained. Moreover, the light-emittingelement easily realizes an emission color which is intended by adesigner, and thus a display device with excellent display quality canbe obtained.

Embodiment Mode 3

In this embodiment mode, electronic devices which include, as a partthereof, the light-emitting device described in Embodiment Mode 2 willbe described. These electronic devices each have a display portionincluding the light-emitting element described in Embodiment Mode 1.

As the electronic devices having the light-emitting element described inEmbodiment Mode 1, the following is given: cameras such as video camerasor digital cameras, goggle type displays, navigation systems, audioreproducing devices (e.g., car audio components and audio components),computers, game machines, portable information terminals (e.g., mobilecomputers, cellular phones, portable game machines, and electronicbooks), and image reproducing devices provided with recording media(specifically, the devices which can reproduce a recording medium suchas a digital versatile disc (DVD) and is provided with a display devicewhich is capable of displaying the reproduced images), and the like.Specific examples of these electronic devices are shown in FIGS. 5A to5D.

FIG. 5A shows a television set of the present invention, which includesa housing 9101, a supporting base 9102, a display portion 9103, speakerportions 9104, video input terminals 9105, and the like. In thistelevision set, the display portion 9103 is manufactured using thelight-emitting element described in Embodiment Mode 1 as a displayelement. Moreover, the television set manufactured using thelight-emitting element whose degree of deterioration with accumulationof driving time is reduced has high reliability of the display portion9103, and the television set provided with the display portion 9103 hashigh reliability. Since the light-emitting element is a light-emittingelement whose degree of deterioration is reduced, deteriorationcompensation function circuits incorporated in the television set can begreatly reduced in size and number.

FIG. 5B shows a computer of the present invention, which includes a mainbody 9201, a housing 9202, a display portion 9203, a keyboard 9204, anexternal connection port 9205, a pointing device 9206, and the like. Inthis computer, the display portion 9203 is manufactured using thelight-emitting element described in Embodiment Mode 1 as a displayelement. Moreover, the computer manufactured using the light-emittingelement whose degree of deterioration with accumulation of driving timeis reduced has high reliability of the display portion 9203, and thecomputer provided with the display portion 9203 has high reliability.Since the light-emitting element is a light-emitting element whosedegree of deterioration is reduced, deterioration compensation functioncircuits incorporated in the computer can be greatly reduced in size andnumber; thus, reduction in size and weight of the computer can beachieved.

FIG. 5C shows a cellular phone of the present invention, which includesa main body 9401, a housing 9402, a display portion 9403, an audio inputportion 9404, an audio output portion 9405, operation keys 9406, anexternal connecting port 9407, an antenna 9408, and the like. In thiscellular phone, the display portion 9403 is manufactured using thelight-emitting element described in Embodiment Mode 1 as a displayelement. Moreover, the cellular phone manufactured using thelight-emitting element whose degree of deterioration with accumulationof driving time is reduced has high reliability of the display portion9403, and the computer provided with the display portion 9403 has highreliability. Since the light-emitting element is a light-emittingelement whose degree of deterioration is reduced, deteriorationcompensation function circuits incorporated in the computer can begreatly reduced in size and number; thus, further reduction in size andweight of the cellular phone can be achieved. The downsized andlightweight cellular phone of the present invention can have appropriatesize and weight even when a variety of additional values are added tothe cellular phone, and thus the cellular phone of the present inventionis suitable for use as a highly functional cellular phone.

FIG. 5D shows a camera of the present invention, which includes a mainbody 9501, a display portion 9502, a housing 9503, an externalconnection port 9504, a remote control receiving portion 9505, an imagereceiving portion 9506, a battery 9507, an audio input portion 9508,operation keys 9509, an eye piece portion 9510, and the like. In thiscamera, the display portion 9502 is manufactured using thelight-emitting element described in Embodiment Mode 1 as a displayelement. Moreover, the camera manufactured using the light-emittingelement whose degree of deterioration with accumulation of driving timeis reduced has high reliability of the display portion 9502, and thecamera provided with the display portion 9502 has high reliability.Since the light-emitting element is a light-emitting element whosedegree of deterioration is reduced, deterioration compensation functioncircuits incorporated in the camera can be greatly reduced in size andnumber; thus, reduction in size and weight of the camera can beachieved.

As described above, the application range of the light-emitting devicemanufactured using the light-emitting element described in EmbodimentMode 1 is so wide that the light-emitting device can be applied toelectronic devices of various fields. Moreover, a display portionmanufactured using the light-emitting element whose degree ofdeterioration with accumulation of driving time is reduced has highreliability, and electronic devices each having the display portion canhave high reliability.

In addition, the light-emitting device of the present invention can alsobe used for a lighting device. One mode of application of thelight-emitting element described in Embodiment mode 1 to a lightingdevice will be described with reference to FIG. 6.

FIG. 6 shows an example of a liquid crystal display device in which thelight-emitting element described in Embodiment Mode 1 is applied as abacklight. The liquid crystal display device shown in FIG. 6 includes ahousing 901, a liquid crystal layer 902, a backlight unit 903, and ahousing 904. The liquid crystal layer 902 is connected to a driver IC905. In addition, the backlight unit 903 is formed using thelight-emitting element described in Embodiment Mode 1, and current issupplied thereto through a terminal 906.

It is desirable that the backlight unit 903 of the liquid crystalexhibit an emission color which becomes suitable light when the light istransmitted through a color filter provided for each pixel and seen byeyes of people who actually watch the liquid crystal display device.That is, although a film which transmits light of red, blue, or green isnormally provided for each pixel as a color filter, transmittance oflight is different depending on the material of the color filter andhuman vision differs depending on the color, and thus the backlightdesirably has desired luminance in a wavelength component of each ofred, blue, and green. In this regard, color balance of thelight-emitting element described in Embodiment Mode 1 is easilyadjusted, and thus the light-emitting element can be used as thebacklight unit 903 of the liquid crystal very preferably.

Note that only one light-emitting element described in Embodiment Mode 1or a plurality of light-emitting elements described in Embodiment Mode 1may be used for the backlight unit 903.

As described above, the light-emitting element described in EmbodimentMode 1 can be applied to the backlight of the liquid crystal displaydevice. The area of the backlight can be increased, and thus the area ofthe liquid crystal display device can be increased. When the backlightis manufactured using the light-emitting element whose degree ofdeterioration with accumulation of driving time is small, the backlightwith high reliability can be obtained. Furthermore, the backlight isthin and a desired emission color can be easily obtained; thus,reduction in thickness of the liquid crystal display device andimprovement in quality of images become possible.

FIG. 7 shows an example in which the light-emitting element described inEmbodiment Mode 1 is used for a desk lamp which is a lighting device.The desk lamp shown in FIG. 7 includes a chassis 2001 and a light source2002, and the light-emitting element described in Embodiment Mode 1 isused for the light source 2002. The light source 2002 may be formed fromone light-emitting element or a plurality of light-emitting elementsdescribed above. Alternatively, the light source 2002 may be formed fromplural types of light-emitting elements which emit different colors. Asdescribed above, the light source 2002 can be manufactured using thelight-emitting element described in Embodiment Mode 1. The light source2002 manufactured using the light-emitting element whose degree ofdeterioration with accumulation of driving time is small has highreliability, and thus the desk lamp provided with the light source 2002also has high reliability. Moreover, since color balance of thelight-emitting element described in Embodiment Mode 1 is easilyadjusted, a desk lamp which has emission colors for purposes, forexample, eye-friendly emission colors, can be easily provided.

FIG. 8 shows an example in which the light-emitting element described inEmbodiment Mode 1 is used for an indoor lighting device 3001. Thelighting device 3001 may be formed from one light-emitting element or aplurality of light-emitting elements described above. Alternatively, thelighting device 3001 may be formed from plural types of light-emittingelements which emit different colors. As described above, the lightingdevice 3001 can be manufactured using the light-emitting elementdescribed in Embodiment Mode 1. The area of the lighting device 3001formed using the light-emitting element can be increased, and thus itcan be used as a large area lighting device. The lighting device 3001manufactured using the light-emitting element having preferable emissionefficiency can be a lighting device which is thin and consumes lesspower. Moreover, the lighting device 3001 manufactured using thelight-emitting element whose degree of deterioration with accumulationof driving time is small can be a lighting device having highreliability. Furthermore, since color balance of the light-emittingelement described in Embodiment Mode 1 is easily adjusted, variousemission colors from warm colors to cold colors can be easily provided.Accordingly, a lighting device which has emission colors for purposes,for example, using a warm color for a living room and using a color witha good color rendering property for a kitchen or a dining room, can beeasily provided.

Embodiment 1

In this embodiment, a manufacturing method and element characteristicsof the light-emitting element described in Embodiment Mode 1 will bedescribed. Note that element structures of light-emitting elements 1 to6 are shown in Table 1.

TABLE 1 Light-Emitting Element 3 6 1 2 (CE) 4 5 (CE) 2nd Electrode Al200 nm  Electron- LiF Injecting  1 nm Layer Electron- Bphen Transporting20 nm Layer Alq 10 nm 1st Layer CzPA:2YGAPPA (1:0.05) 20 nm 2nd LayerYGAPA:rubrene (1:0.0025) PCCPA:rubrene (1:0.0025) 10 nm 3rd LayerDPAnth:2YGAPPA — DPAnth:2YGAPPA — (1:0.1) (1:0.1) 10 nm 20 nm 10 nm 20nm Hole- NPB Transporting 10 nm Layer Hole- NPB:MoOx (4:1) Injecting 50nm Layer 1st Electrode ITSO 110 nm (Light-Emitting Element 1)

First, silicon or indium tin oxide containing silicon oxide wasdeposited to a thickness of 110 nm over a glass substrate by asputtering method to form a first electrode (electrode area: 2 mm×2 mm).

Next, the substrate over which the first electrode had been formed wasfixed to a substrate holder provided in a vacuum evaporation apparatusso that a surface of the substrate over which the first electrode hadbeen formed faced downward, and the pressure was reduced to about 10⁻⁴Pa, and then 4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (NPB) andmolybdenum(VI) oxide were co-evaporated, whereby a layer containing acomposite material in which an organic compound and an inorganiccompound were combined was formed. The thickness of the layer was 50 nmand the weight ratio between NPB and molybdenum(VI) oxide was adjustedto be 4:1 (=NPB:molybdenum oxide). Note that the co-evaporation methodis an evaporation method in which evaporation is carried out from aplurality of evaporation sources at the same time in one treatmentchamber.

Subsequently, NPB was deposited to a thickness of 10 nm by anevaporation method using resistance heating to form a hole-transportinglayer.

After that, 9,10-diphenylanthracene (DPAnth) and4-(9H-carbazol-9-yl)-4′-(9,10-diphenyl-2-anthryl)triphenylamine(2YGAPPA) were co-evaporated to form a third layer with a thickness of10 nm. Here, the weight ratio between DPAnth and 2YGAPPA was adjusted tobe 1:0.1 (=DPAnth:2YGAPPA).

Then, 4-(9H-carbazol-9-yl)-4′-(10-phenyl-9-anthryl)triphenylamine(YGAPA) and rubrene were co-evaporated to form a second layer with athickness of 10 nm. Here, the weight ratio between YGAPA and rubrene wasadjusted to be 1:0.0025 (=YGAPA:rubrene).

Furthermore, 9-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazole (CzPA) and2YGAPPA were co-evaporated to form a first layer with a thickness of 20nm. Here, the weight ratio between CzPA and 2YGAPPA was adjusted to be1:0.05 (=CzPA:2YGAPPA).

After that, by an evaporation method using resistance heating,tris(8-quinolinolato)aluminum (Alq) was deposited to a thickness of 10nm, and then bathophenanthroline (BPhen) was deposited to a thickness of20 nm to form an electron-transporting layer.

Then, in a similar manner, by an evaporation method using resistanceheating, lithium fluoride (LiF) was deposited to a thickness of about 1nm to form an electron-injecting layer. Finally, aluminum was depositedto a thickness of 200 nm to form a second electrode. Accordingly, thelight-emitting element 1 was manufactured.

The light-emitting element 1 obtained through the above-described stepswas sealed in a glove box containing a nitrogen atmosphere so as not tobe exposed to atmospheric air. Then, the operation characteristics ofthe light-emitting element 1 were measured. The measurement was carriedout at room temperature (under an atmosphere maintaining 25° C.).

FIG. 9 shows current density-luminance characteristics of thelight-emitting element 1. FIG. 10 shows luminance-current efficiencycharacteristics. FIG. 11 shows voltage-luminance characteristics. FIG.12 shows voltage-current characteristics. FIG. 13 shows an emissionspectrum upon feeding a current of 1 mA to the light-emitting element 1.

In the light-emitting element 1, 2YGAPPA which is an emission centersubstance of the first layer and the third layer emits blue light andrubrene which is an emission center substance of the second layer emitsyellow light. That is, according to FIG. 13, it is found that lightemission having a peak near 462 nm is light emission of 2YGAPPA; lightemission having a peak near 549 nm is light emission of rubrene; and asfor the light-emitting element 1, the intensity of the light emission of2YGAPPA on the shorter wavelength side and the intensity of the lightemission of rubrene on the longer wavelength side are almost the same.In a conventional structure, light emission on the longer wavelengthside is higher due to influence of energy transfer and it is difficultto balance emission colors. However, with use of the structure of thepresent invention, like the light-emitting element 1 described above,the emission intensity on the shorter wavelength side and the emissionintensity on the longer wavelength side can be made equal, and itbecomes possible to easily adjust balance of emission colors. Note thatthe CIE chromaticity coordinate of the light-emitting element 1 at aluminance of 900 cd/m² was (x=0.26, y=0.35), and the emission color waswhite.

(Light-Emitting Element 2)

First, silicon or indium tin oxide containing silicon oxide wasdeposited to a thickness of 110 nm over a glass substrate by asputtering method to form a first electrode (electrode area: 2 mm×2 mm).

Next, the substrate over which the first electrode had been formed wasfixed to a substrate holder provided in a vacuum evaporation apparatusso that a surface of the substrate over which the first electrode hadbeen formed faced downward, and the pressure was reduced to about 10⁻⁴Pa, and then NPB and molybdenum(VI) oxide were co-evaporated, whereby alayer containing a composite material in which an organic compound andan inorganic compound were combined was formed. The thickness of thelayer was 50 nm and the weight ratio between NPB and molybdenum(VI)oxide was adjusted to be 4:1 (=NPB:molybdenum oxide). Note that theco-evaporation method is an evaporation method in which evaporation iscarried out from a plurality of evaporation sources at the same time inone treatment chamber.

Subsequently, NPB was deposited to a thickness of 10 nm by anevaporation method using resistance heating to form a hole-transportinglayer.

After that, DPAnth and 2YGAPPA were co-evaporated to form a third layerwith a thickness of 20 nm. Here, the weight ratio between DPAnth and2YGAPPA was adjusted to be 1:0.1 (=DPAnth:2YGAPPA).

Then, YGAPA and rubrene were co-evaporated to form a second layer with athickness of 10 nm. Here, the weight ratio between YGAPA and rubrene wasadjusted to be 1:0.0025 (=YGAPA:rubrene).

Furthermore, CzPA and 2YGAPPA were co-evaporated to form a first layerwith a thickness of 20 nm. Here, the weight ratio between CzPA and2YGAPPA was adjusted to be 1:0.05 (=CzPA:2YGAPPA).

After that, by an evaporation method using resistance heating, Alq wasdeposited to a thickness of 10 nm, and then BPhen was deposited to athickness of nm to form an electron-transporting layer.

Then, in a similar manner, by an evaporation method using resistanceheating, lithium fluoride (LiF) was deposited to a thickness of about 1nm to form an electron-injecting layer. Finally, aluminum was depositedto a thickness of 200 nm to form a second electrode. Accordingly, thelight-emitting element 2 was manufactured.

The light-emitting element 2 obtained through the above-described stepswas sealed in a glove box containing a nitrogen atmosphere so as not tobe exposed to atmospheric air. Then, the operation characteristics ofthe light-emitting element 2 were measured. The measurement was carriedout at room temperature (under an atmosphere maintaining 25° C.).

FIG. 14 shows current density-luminance characteristics of thelight-emitting element 2. FIG. 15 shows luminance-current efficiencycharacteristics. FIG. 16 shows voltage-luminance characteristics. FIG.17 shows voltage-current characteristics. FIG. 18 shows an emissionspectrum upon feeding a current of 1 mA to the light-emitting element 2.

In the light-emitting element 2, 2YGAPPA which is an emission centersubstance of the first layer and the third layer emits blue light andrubrene which is an emission center substance of the second layer emitsyellow light. That is, according to FIG. 18, it is found that lightemission having a peak near 462 nm is light emission of 2YGAPPA; lightemission having a peak near 549 nm is light emission of rubrene; and asfor the light-emitting element 2, the intensity of the light emission of2YGAPPA on the shorter wavelength side is higher than the intensity ofthe light emission of rubrene on the longer wavelength side. In aconventional structure, light emission on the longer wavelength side ishigher due to influence of energy transfer and it is difficult tobalance emission colors. However, with use of the structure of thepresent invention, like the light-emitting element 2 described above,the emission intensity on the shorter wavelength side can be higher thanthe emission intensity on the longer wavelength side, and it becomespossible to easily adjust balance of emission colors. Note that the CIEchromaticity coordinate of the light-emitting element 2 at a luminanceof 780 cd/m² was (x=0.26, y=0.34), and the emission color was white.

(Light-Emitting Element 3)

As the light-emitting element 3, which is used as a comparative example(CE) of the light-emitting element 1 and the light-emitting element 2, alight-emitting element in which a third layer was not formed, that is, alight-emitting element having the structure of the light-emittingelement 115 described as the conventional example in Embodiment Mode 1was manufactured. First, silicon or indium tin oxide containing siliconoxide was deposited to a thickness of 110 nm over a glass substrate by asputtering method to form a first electrode (electrode area: 2 mm×2 mm).

Next, the substrate over which the first electrode had been formed wasfixed to a substrate holder provided in a vacuum evaporation apparatusso that a surface of the substrate over which the first electrode hadbeen formed faced downward, and the pressure was reduced to about 10⁻⁴Pa, and then NPB and molybdenum(VI) oxide were co-evaporated, whereby alayer containing a composite material in which an organic compound andan inorganic compound were combined was formed. The thickness of thelayer was 50 nm and the weight ratio between NPB and molybdenum(VI)oxide was adjusted to be 4:1 (=NPB:molybdenum oxide). Note that theco-evaporation method is an evaporation method in which evaporation iscarried out from a plurality of evaporation sources at the same time inone treatment chamber.

Subsequently, NPB was deposited to a thickness of 10 nm by anevaporation method using resistance heating to form a hole-transportinglayer.

Then, YGAPA and rubrene were co-evaporated to form a second layer with athickness of 10 nm. Here, the weight ratio between YGAPA and rubrene wasadjusted to be 1:0.0025 (=YGAPA:rubrene).

Furthermore, CzPA and 2YGAPPA were co-evaporated to form a first layerwith a thickness of 20 nm. Here, the weight ratio between CzPA and2YGAPPA was adjusted to be 1:0.05 (=CzPA:2YGAPPA).

After that, by an evaporation method using resistance heating, Alq wasdeposited to a thickness of 10 nm, and then BPhen was deposited to athickness of nm to form an electron-transporting layer.

Then, in a similar manner, by an evaporation method using resistanceheating, lithium fluoride (LiF) was deposited to a thickness of about 1nm to form an electron-injecting layer. Finally, aluminum was depositedto a thickness of 200 nm to form a second electrode. Accordingly, thelight-emitting element 3 was manufactured.

The light-emitting element 3 obtained through the above-described stepswas sealed in a glove box containing a nitrogen atmosphere so as not tobe exposed to atmospheric air. Then, the operation characteristics ofthe light-emitting element 3 were measured. The measurement was carriedout at room temperature (under an atmosphere maintaining 25° C.).

FIG. 19 shows an emission spectrum of the light-emitting element 3. Inthe light-emitting element 3, 2YGAPPA which is an emission centersubstance of the first layer emits blue light and rubrene which is anemission center substance of the second layer emits yellow light. Thatis, according to FIG. 19, it is found that light emission having a peaknear 465 nm is light emission of 2YGAPPA; light emission having a peaknear 549 nm is light emission of rubrene; and as for the light-emittingelement 3, the intensity of the light emission of rubrene on the longerwavelength side is higher than the intensity of the light emission of2YGAPPA on the shorter wavelength side. Here, with reference to thestructure of the second layer, YGAPA and rubrene was co-evaporated at aratio of 1:0.0025, and this is the lowest level of the concentration ofrubrene which can be controlled by the inventor at the moment. In otherwords, it is found that even if the concentration of rubrene is made aslow as possible, light emission of rubrene having an emission color onthe longer wavelength side is higher, and it is difficult to controlemission colors in a conventional structure. Note that the CIEchromaticity coordinate of the light-emitting element 3 at a luminanceof 1740 cd/m² was (x=0.28, y=0.38), and the emission color was bluewhite.

Next, evaluation results on reliability are shown. FIG. 20 shows timedependence of normalized luminance of the light-emitting element 1 andthe light-emitting element 3 when the light-emitting element 1 and thelight-emitting element 3 were driven at an initial luminance of 1000cd/m² and constant current density. Note that, in the graph, the thickline represents the result of the light-emitting element 1 and the thinline represents the result of the light-emitting element 3. Alsoaccording to FIG. 20, it is found that decrease in luminance of thelight-emitting element 1 is suppressed more than that of thelight-emitting element 3 which is the comparative example (CE). Notethat the luminance of the light-emitting element 3 decreased to 53% in590 hours, whereas the luminance of the light-emitting element 1 was 54%in 1100 hours, which means the life of the light-emitting element 1 istwice as long as the light-emitting element 3.

(Light-Emitting Element 4)

First, silicon or indium tin oxide containing silicon oxide wasdeposited to a thickness of 110 nm over a glass substrate by asputtering method to form a first electrode (electrode area: 2 mm×2 mm).

Next, the substrate over which the first electrode had been formed wasfixed to a substrate holder provided in a vacuum evaporation apparatusso that a surface of the substrate over which the first electrode wasformed faced downward, and the pressure had been reduced to about 10⁻⁴Pa, and then NPB and molybdenum(VI) oxide were co-evaporated, whereby alayer containing a composite material in which an organic compound andan inorganic compound were combined was formed. The thickness of thelayer was 50 nm and the weight ratio between NPB and molybdenum(VI)oxide was adjusted to be 4:1 (=NPB:molybdenum oxide). Note that theco-evaporation method is an evaporation method in which evaporation iscarried out from a plurality of evaporation sources at the same time inone treatment chamber.

Subsequently, NPB was deposited to a thickness of 10 nm by anevaporation method using resistance heating to form a hole-transportinglayer.

After that, DPAnth and 2YGAPPA were co-evaporated to form a third layerwith a thickness of 10 nm. Here, the weight ratio between DPAnth and2YGAPPA was adjusted to be 1:0.1 (=DPAnth:2YGAPPA).

Then, 9-phenyl-9′-[4-(10-phenyl-9-anthryl)phenyl]-3,3′-bi(9H-carbazole)(PCCPA) and rubrene were co-evaporated to form a second layer with athickness of nm. Here, the weight ratio between PCCPA and rubrene wasadjusted to be 1:0.0025 (=PCCPA:rubrene).

Furthermore, CzPA and 2YGAPPA were co-evaporated to form a first layerwith a thickness of 20 nm. Here, the weight ratio between CzPA and2YGAPPA was adjusted to be 1:0.05 (=CzPA:2YGAPPA).

After that, by an evaporation method using resistance heating, Alq wasdeposited to a thickness of 10 nm, and then BPhen was deposited to athickness of nm to form an electron-transporting layer.

Then, in a similar manner, by an evaporation method using resistanceheating, lithium fluoride (LiF) was deposited to a thickness of about 1nm to form an electron-injecting layer. Finally, aluminum was depositedto a thickness of 200 nm to form a second electrode. Accordingly, thelight-emitting element 4 was manufactured.

The light-emitting element 4 obtained through the above-described stepswas sealed in a glove box containing a nitrogen atmosphere so as not tobe exposed to atmospheric air. Then, the operation characteristics ofthe light-emitting element 4 were measured. The measurement was carriedout at room temperature (under an atmosphere maintaining 25° C.).

FIG. 21 shows current density-luminance characteristics of thelight-emitting element 4. FIG. 22 shows luminance-current efficiencycharacteristics. FIG. 23 shows voltage-luminance characteristics. FIG.24 shows voltage-current characteristics. FIG. 25 shows an emissionspectrum upon feeding a current of 1 mA to the light-emitting element 4.

In the light-emitting element 4, 2YGAPPA which is an emission centersubstance of the first layer and the third layer emits blue light andrubrene which is an emission center substance of the second layer emitsyellow light. That is, according to FIG. 25, it is found that lightemission having a peak near 462 nm is light emission of 2YGAPPA; lightemission having a peak near 549 nm is light emission of rubrene; and asfor the light-emitting element 4, the intensity of the light emission of2YGAPPA on the shorter wavelength side is higher than the intensity ofthe light emission of rubrene on the longer wavelength side. In aconventional structure, light emission on the longer wavelength side ishigher due to influence of energy transfer and it is difficult tobalance emission colors. However, with use of the structure of thepresent invention, like the light-emitting element 4 described above,the emission intensity on the shorter wavelength side can be higher thanthe emission intensity on the longer wavelength side, and it becomespossible to easily adjust balance of emission colors. Note that the CIEchromaticity coordinate of the light-emitting element 4 at a luminanceof 810 cd/m² was (x=0.25, y=0.34), and the emission color was bluishwhite.

(Light-Emitting Element 5)

First, silicon or indium tin oxide containing silicon oxide wasdeposited to a thickness of 110 nm over a glass substrate by asputtering method to form a first electrode (electrode area: 2 mm×2 mm).

Next, the substrate over which the first electrode had been formed wasfixed to a substrate holder provided in a vacuum evaporation apparatusso that a surface of the substrate over which the first electrode hadbeen formed faced downward, and the pressure was reduced to about 10⁻⁴Pa, and then NPB and molybdenum(VI) oxide were co-evaporated, whereby alayer containing a composite material in which an organic compound andan inorganic compound were combined was formed. The thickness of thelayer was 50 nm and the weight ratio between NPB and molybdenum(VI)oxide was adjusted to be 4:1 (=NPB:molybdenum oxide). Note that theco-evaporation method is an evaporation method in which evaporation iscarried out from a plurality of evaporation sources at the same time inone treatment chamber.

Subsequently, NPB was deposited to a thickness of 10 nm by anevaporation method using resistance heating to form a hole-transportinglayer.

After that, DPAnth and 2YGAPPA were co-evaporated to form a third layerwith a thickness of 20 nm. Here, the weight ratio between DPAnth and2YGAPPA was adjusted to be 1:0.1 (=DPAnth:2YGAPPA).

Then, PCCPA and rubrene were co-evaporated to form a second layer with athickness of 10 nm. Here, the weight ratio between PCCPA and rubrene wasadjusted to be 1:0.0025 (=PCCPA:rubrene).

Furthermore, CzPA and 2YGAPPA were co-evaporated to form a first layerwith a thickness of 20 nm. Here, the weight ratio between CzPA and2YGAPPA was adjusted to be 1:0.05 (=CzPA:2YGAPPA).

After that, by an evaporation method using resistance heating, Alq wasdeposited to a thickness of 10 nm, and then BPhen was deposited to athickness of nm to form an electron-transporting layer.

Then, in a similar manner, by an evaporation method using resistanceheating, lithium fluoride (LiF) was deposited to a thickness of about 1nm to form an electron-injecting layer. Finally, aluminum was depositedto a thickness of 200 nm to form a second electrode. Accordingly, thelight-emitting element 5 was manufactured.

The light-emitting element 5 obtained through the above-described stepswas sealed in a glove box containing a nitrogen atmosphere so as not tobe exposed to atmospheric air. Then, the operation characteristics ofthe light-emitting element 5 were measured. The measurement was carriedout at room temperature (under an atmosphere maintaining 25° C.).

FIG. 26 shows current density-luminance characteristics of thelight-emitting element 5. FIG. 27 shows luminance-current efficiencycharacteristics. FIG. 28 shows voltage-luminance characteristics. FIG.29 shows voltage-current characteristics. FIG. 30 shows an emissionspectrum upon feeding a current of 1 mA to the light-emitting element 5.

In the light-emitting element 5, 2YGAPPA which is an emission centersubstance of the first layer and the third layer emits blue light andrubrene which is an emission center substance of the second layer emitsyellow light. That is, according to FIG. 30, it is found that lightemission having a peak near 462 nm is light emission of 2YGAPPA; lightemission having a peak near 549 nm is light emission of rubrene; and asfor the light-emitting element 5, the intensity of the light emission of2YGAPPA on the shorter wavelength side is higher than the intensity ofthe light emission of rubrene on the longer wavelength side. In aconventional structure, light emission on the longer wavelength side ishigher due to influence of energy transfer and it is difficult tobalance emission colors. However, with use of the structure of thepresent invention, like the light-emitting element 5 described above,the emission intensity on the shorter wavelength side can be higher thanthe emission intensity on the longer wavelength side, and it becomespossible to easily adjust balance of emission colors. Note that the CIEchromaticity coordinate of the light-emitting element 5 at a luminanceof 890 cd/m² was (x=0.25, y=0.33), and the emission color was slightlybluish white.

(Light-Emitting Element 6)

As the light-emitting element 6, which is used as a comparative example(CE) of the light-emitting element 4 and the light-emitting element 5, alight-emitting element in which a third layer was not formed wasmanufactured. First, silicon or indium tin oxide containing siliconoxide was deposited to a thickness of 110 nm over a glass substrate by asputtering method to form a first electrode (electrode area: 2 mm×2 mm).

Next, the substrate over which the first electrode had been formed wasfixed to a substrate holder provided in a vacuum evaporation apparatusso that a surface of the substrate over which the first electrode wasformed faced downward, and the pressure was reduced to about 10⁻⁴ Pa,and then NPB and molybdenum(VI) oxide were co-evaporated, whereby alayer containing a composite material in which an organic compound andan inorganic compound were combined was formed. The thickness of thelayer was 50 nm and the weight ratio between NPB and molybdenum(VI)oxide was adjusted to be 4:1 (=NPB:molybdenum oxide). Note that theco-evaporation method is an evaporation method in which evaporation iscarried out from a plurality of evaporation sources at the same time inone treatment chamber.

Subsequently, NPB was deposited to a thickness of 10 nm by anevaporation method using resistance heating to form a hole-transportinglayer.

Then, PCCPA and rubrene were co-evaporated to form a second layer with athickness of 10 nm. Here, the weight ratio between PCCPA and rubrene wasadjusted to be 1:0.0025 (=PCCPA:rubrene).

Furthermore, CzPA and 2YGAPPA were co-evaporated to form a first layerwith a thickness of 20 nm. Here, the weight ratio between CzPA and2YGAPPA was adjusted to be 1:0.05 (=CzPA:2YGAPPA).

After that, by an evaporation method using resistance heating, Alq wasdeposited to a thickness of 10 nm, and then BPhen was deposited to athickness of nm to form an electron-transporting layer.

Then, in a similar manner, by an evaporation method using resistanceheating, lithium fluoride (LiF) was deposited to a thickness of about 1nm to form an electron-injecting layer. Finally, aluminum was depositedto a thickness of 200 nm to form a second electrode. Accordingly, thelight-emitting element 6 was manufactured.

The light-emitting element 6 obtained through the above-described stepswas sealed in a glove box containing a nitrogen atmosphere so as not tobe exposed to atmospheric air. Then, the operation characteristics ofthe light-emitting element 6 were measured. The measurement was carriedout at room temperature (under an atmosphere maintaining 25° C.).

FIG. 31 shows an emission spectrum of the light-emitting element 6. Inthe light-emitting element 6, 2YGAPPA which is an emission centersubstance of the first layer emits blue light and rubrene which is anemission center substance of the second layer emits yellow light. Thatis, according to FIG. 31, it is found that light emission having a peaknear 465 nm is light emission of 2YGAPPA; light emission having a peaknear 549 nm is light emission of rubrene; and as for the light-emittingelement 6, the intensity of the light emission of rubrene on the longerwavelength side is higher than the intensity of the light emission of2YGAPPA on the shorter wavelength side. Note that the CIE chromaticitycoordinate of the light-emitting element 6 at a luminance of 1520 cd/m²was (x=0.28, y=0.36), and the emission color was slightly bluish white.

Next, evaluation results on reliability are shown. FIG. 32 shows timedependence of normalized luminance of the light-emitting element 4 andthe light-emitting element 6 when the light-emitting element 4 and thelight-emitting element 6 were driven at an initial luminance of 1000cd/m² and constant current density. Note that, in the graph, the thickline represents the result of the light-emitting element 4 and the thinline represents the result of the light-emitting element 6. Alsoaccording to FIG. 32, it is found that decrease in luminance of thelight-emitting element 4 is suppressed more than decrease in luminanceof the light-emitting element 6 which is the comparative example (CE).Note that the luminance of the light-emitting element 6 decreased to 58%in 590 hours, whereas the luminance of the light-emitting element 4 was61% in 1100 hours, which means the life of the light-emitting element 4is twice as long as the light-emitting element 6.

Embodiment 2

In this embodiment, a manufacturing method and element characteristicsof the light-emitting element described in Embodiment Mode 1 will bedescribed. Note that element structures of light-emitting elements 7 and8 are shown in Table 2.

TABLE 2 Light-Emitting Element 7 8 2nd Electrode Al 200 nmElectron-Injecting LiF Layer 1 nm Electron-Transporting Bphen Layer 20nm Alq 10 nm 1st Layer CzPA:PCBAPA (1:0.05) 20 nm 2nd Layer PCCPA:2PCAPA(1:0.005) PCBAPA:2PCAPA (1:0.02) 10 nm 3rd Layer PCCPA:PCBAPA (1:0.1) 10nm Hole-Transporting NPB Layer 10 nm Hole-Injecting Layer NPB:MoOx (4:1)50 nm 1^(st) Electrode ITSO 110 nm(Light-Emitting Element 7)

First, silicon or indium tin oxide containing silicon oxide wasdeposited to a thickness of 110 nm over a glass substrate by asputtering method to form a first electrode (electrode area: 2 mm×2 mm).

Next, the substrate over which the first electrode had been formed wasfixed to a substrate holder provided in a vacuum evaporation apparatusso that a surface of the substrate over which the first electrode hadbeen formed faced downward, and the pressure was reduced to about 10⁻⁴Pa, and then 4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (NPB) andmolybdenum(VI) oxide were co-evaporated, whereby a layer containing acomposite material in which an organic compound and an inorganiccompound were combined was formed. The thickness of the layer was 50 nmand the weight ratio between NPB and molybdenum(VI) oxide was adjustedto be 4:1 (=NPB:molybdenum oxide). Note that the co-evaporation methodis an evaporation method in which evaporation is carried out from aplurality of evaporation sources at the same time in one treatmentchamber.

Subsequently, NPB was deposited to a thickness of 10 nm by anevaporation method using resistance heating to form a hole-transportinglayer.

After that,9-phenyl-9′-[4-(10-phenyl-9-anthryl)phenyl]-3,3′-bi(9H-carbazole)(PCCPA) and4-(10-phenyl-9-anthryl)4′-(9-phenyl-9H-carbazol-3-yl)triphenylamine(PCBAPA) were co-evaporated to form a third layer with a thickness of 10nm. Here, the weight ratio between PCCPA and PCBAPA was adjusted to be1:0.1 (=PCCPA:PCBAPA).

Then, PCCPA andN-(9,10-diphenyl-2-anthryl)-N,9-diphenyl-9H-carbazol-3-amine (2PCAPA)were co-evaporated to form a second layer with a thickness of 10 nm.Here, the weight ratio between PCCPA and 2PCAPA was adjusted to be1:0.005 (=PCCPA:2PCAPA).

Furthermore, CzPA and PCBAPA were co-evaporated to form a first layerwith a thickness of 20 nm. Here, the weight ratio between CzPA andPCBAPA was adjusted to be 1:0.05 (=CzPA:PCBAPA).

After that, by an evaporation method using resistance heating,tris(8-quinolinolato)aluminum (Alq) was deposited to a thickness of 10nm, and then bathophenanthroline (BPhen) was deposited to a thickness of20 nm to form an electron-transporting layer.

Then, in a similar manner, by an evaporation method using resistanceheating, lithium fluoride (LiF) was deposited to a thickness of about 1nm to form an electron-injecting layer. Finally, aluminum was depositedto a thickness of 200 nm to form a second electrode. Accordingly, thelight-emitting element 7 was manufactured.

The light-emitting element 7 obtained through the above-described stepswas sealed in a glove box containing a nitrogen atmosphere so as not tobe exposed to atmospheric air. Then, the operation characteristics weremeasured. The measurement was carried out at room temperature (under anatmosphere maintaining 25° C.).

FIG. 33 shows current density-luminance characteristics of thelight-emitting element 7. FIG. 34 shows luminance-current efficiencycharacteristics. FIG. 35 shows voltage-luminance characteristics. FIG.36 shows voltage-current characteristics. FIG. 37 shows an emissionspectrum upon feeding a current of 1 mA to the light-emitting element 7.

In the light-emitting element 7, PCBAPA which is an emission centersubstance of the first layer and the third layer emits blue light and2PCAPA which is an emission center substance of the second layer emitsgreen light. That is, according to FIG. 37, it is found that lightemission having a peak near 466 nm is light emission of PCBAPA; lightemission having a peak near 493 nm is light emission of 2PCAPA; and asfor the light-emitting element 7, the intensity of the light emission ofPCBAPA on the shorter wavelength side and the intensity of the lightemission of 2PCAPA on the longer wavelength side are almost the same. Ina conventional structure, light emission on the longer wavelength sideis higher due to influence of energy transfer and it is difficult tobalance emission colors. However, with use of the structure of thepresent invention, like the light-emitting element 7 described above,the emission intensity on the shorter wavelength side and the emissionintensity on the longer wavelength side can be made equal, and itbecomes possible to easily adjust balance of emission colors. Note thatthe CIE chromaticity coordinate of the light-emitting element 7 at aluminance of 1100 cd/m² was (x=0.18, y=0.27), and the emission color wasblue green.

(Light-Emitting Element 8)

As for the manufacture of a light-emitting element 8, the steps upthrough formation of a third layer were performed in a similar manner tothe steps of the light-emitting element 7.

Subsequently, PCBAPA and 2PCAPA were co-evaporated to form a secondlayer with a thickness of 10 nm. Here, the weight ratio between PCBAPAand 2PCAPA was adjusted to be 1:0.02 (=PCBAPA: 2PCAPA).

After that, the steps of formation of from a first layer to a cathodewere performed in a similar manner to the steps of the light-emittingelement 7. Accordingly, the light-emitting element 8 was manufactured.

The light-emitting element 8 obtained through the above-described stepswas sealed in a glove box containing a nitrogen atmosphere so as not tobe exposed to atmospheric air. Then, the operation characteristics weremeasured. The measurement was carried out at room temperature (under anatmosphere maintaining 25° C.).

FIG. 38 shows current density-luminance characteristics of thelight-emitting element 8. FIG. 39 shows luminance-current efficiencycharacteristics. FIG. 40 shows voltage-luminance characteristics. FIG.41 shows voltage-current characteristics. FIG. 42 shows an emissionspectrum upon feeding a current of 1 mA to the light-emitting element 8.

In the light-emitting element 8, PCBAPA which is an emission centersubstance of the first layer and the third layer emits blue light and2PCAPA which is an emission center substance of the second layer emitsgreen light. That is, according to FIG. 42, light emission having a peaknear 470 nm is light emission of PCBAPA, and light emission having apeak near 500 nm is light emission of 2PCAPA. As described above, it canbe said that the light-emitting element of the present invention is alsocapable of emitting light of high intensity of an emission centersubstance on the longer wavelength side and capable of easily adjustingbalance of emission colors. Note that the CIE chromaticity coordinate ofthe light-emitting element 8 at a luminance of 1190 cd/m² was (x=0.20,y=0.33), and the emission color was blue green.

Note that by formation of a light-emitting element having, as a layercontaining an organic compound, a stacked-layer structure (stackedstructure including the hole-injecting layer to the electron-injectinglayer) which provides blue green emission and a stacked-layer structurewhich provides red emission, a light-emitting element which emits whitelight can be provided. At this time, a charge generation layer isprovided between the stacked layer which provides blue green emissionand the stacked layer which provides red emission. The charge generationlayer can be formed of the composite material described in EmbodimentMode 1. In addition, the charge generation layer may have a stackedstructure of a layer formed of the composite material and a layer formedof another material. In that case, as the layer formed of anothermaterial, a layer containing a substance having an electron donatingproperty and a substance having a high electron-transporting property,or a layer formed of a transparent conductive film can be used. As for alight-emitting element having such a structure, even when red emissionis phosphorescence and blue green emission is fluorescence, problemssuch as energy transfer and quenching are unlikely to occur, and a whitelight-emitting element which has both high light emission efficiency andlong life can be easily obtained due to expansion in the range ofselection of materials. Moreover, since blue green emission can beeasily adjusted, there is an advantage in that white emission with adesired color can be easily obtained.

Reference Example

Since 2YGAPPA used for the light-emitting elements 1 to 6 is not a knownsubstance, a synthetic method thereof will be described. Note that2YGAPPA is represented by the following structural formula (1).

[Step 1] Synthesis of 2-bromo-9,10-diphenylanthracene (i) Synthesis of2-bromo-9,10-anthraquinone

A synthesis scheme of 2-bromo-9,10-anthraquinone is shown in (A-1).

46 g (0.20 mol) of copper(II) bromide and 500 mL of acetonitrile wereput into a 1 L three-neck flask. Then, 17 g (0.17 mol) of tert-butylnitrite was added thereto. The mixture was heated to 65° C. 25 g (0.11mol) of 2-amino-9,10-anthraquinone was added to the mixture, and themixture was stirred at the same temperature for six hours. Afterreaction, a reaction solution was poured into 500 mL of hydrochrolicacid with 3 mol/L, and this suspension was stirred for three hours, sothat a solid substance was precipitated. The precipitate was collectedby suction filtration, and washed with water and ethanol while beingsuction-filtrated. The precipitate was dissolved in toluene. The mixturewas suction-filtrated through Florisil (produced by Wako Pure ChemicalIndustries, Ltd., Catalog No. 540-00135), Celite (produced by Wako PureChemical Industries, Ltd., Catalog No. 531-16855), and alumina. Theobtained filtrate was concentrated, so that a solid substance wasobtained. This solid substance was recrystallized with a mixed solventof chloroform and hexane, so that 18.6 g of 2-bromo-9,10-anthraquinoneas a milky white powdered solid substance, which was an object, wasobtained in a yield of 58%.

ii) Synthesis of 2-bromo-9,10-diphenyl-9,10-dihydroanthracene-9,10-diol

A synthesis scheme of2-bromo-9,10-diphenyl-9,10-dihydroanthracene-9,10-diol is shown in(A-2).

4.9 g (17 mmol) of 2-bromo-9,10-anthraquinone was put into a 300 mLthree-neck flask. The atmosphere in the flask was substituted withnitrogen. 100 mL of tetrahydrofuran (THF) was added and dissolved well.After that, 18 mL (37 mmol) of phenyl lithium was dripped into thesolution, and the mixture was stirred at room temperature for about 12hours. After the reaction, the solution was washed with water. Then, theaqueous layer was extracted with ethyl acetate. The extracted solutionand an organic layer were mixed to be dried with magnesium sulfate.After the drying, this mixture was suction-filtrated and the filtratewas concentrated, so that2-bromo-9,10-diphenyl-9,10-dihydroanthracene-9,10-diol (about 7.6 g),which was an object, was obtained.

(iii) Synthesis of 2-bromo-9,10-diphenylanthracene

A synthesis scheme of 2-bromo-9,10-diphenylanthracene is shown in (A-3).

About 7.6 g (17 mmol) of 2-bromo-9,10-diphenyl-9,10-dihydroanthracene-9,10-diol, which was obtained, 5.1 g (31 mmol) of potassium iodide, 9.7 g(92 mmol) of sodium phosphinate monohydrate, and 50 mL of glacial aceticacid were put into a 500 mL three-neck flask. The mixture was refluxedat 120° C. for two hours. After that, 30 mL of 50% phosphinic acid wasadded to the mixture, and the mixture was stirred at 120° C. for onehour. After the reaction, the solution was washed with water. Then, anaqueous layer was extracted with ethyl acetate. The extracted solutionand an organic layer were mixed to be dried with magnesium sulfate.After the drying, this mixture was suction-filtrated and the filtratewas concentrated, so that a solid substance was obtained. This solidsubstance was dissolved in toluene, and then the mixture was filteredthrough Celite, Florisil, and then alumina. The obtained filtrate wasconcentrated to obtain a solid substance, and the solid substance wasrecrystallized with a mixed solvent of chloroform and hexane, so that5.1 g of 2-bromo-9,10-diphenylanthracene as a light yellow powderedsolid substance, which was an object, was obtained. The yield of the twostages (ii) and (iii) was 74%.

[Step 2] Synthesis of 2-(4-bromophenyl)-9,10-diphenylantracene (i)Synthesis of 2-iodo-9,10-diphenylanthracene

Synthesis scheme of 2-iodo-9,10-diphenylanthracene is shown in (A-4).

10 g (24 mmol) of 2-bromo-9,10-diphenylanthracene was put into a 500 mLthree-neck flask, the atmosphere in the flask was substituted withnitrogen, and then 150 mL of tetrahydrofuran was added thereto anddissolved well. This solution was stirred at −78° C. 19 mL ofn-butyllithium solution (1.6 mmol/L) was dropped into this solution witha syringe and the mixture was stirred at −78° C. for one hour, so that awhite solid substance was precipitated. After reaction, a solution inwhich 12 g (49 mmol) of iodine was dissolved into 80 mL oftetrahydrofuran was dropped into this reacted mixture with use of adropping funnel. After the dropping, the mixture was stirred at −78° C.for one hour and at room temperature for 12 hours. After reaction, asodium thiosulfate solution was added into the reaction solution, andwas stirred at room temperature for one hour. Ethyl acetate was addedinto this mixture for extraction. An aqueous layer and an organic layerwere separated, and the organic layer was washed with sodium thiosulfatesolution and saturated saline in this order. The aqueous layer and theorganic layer were separated and the organic layer was dried withmagnesium sulfate. This mixture was suction-filtrated to remove themagnesium sulfate. The obtained filtrate was concentrated, so that asolid substance was obtained. Methanol was added into this solidsubstance and washed by ultrasonic wave irradiation, so that a solidsubstance was precipitated. This solid substance was collected bysuction filtration, so that 9.9 g of a light yellow powdered solidsubstance was obtained in a yield of 90%.

(ii) Synthesis of 2-(4-bromophenyl)-9,10-diphenylanthracene

Synthesis scheme of 2-(4-bromophenyl)-9,10-diphenylanthracene is shownin (A-5).

2.0 g (9.9 mmol) of 4-bromophenyl boronic acid, 0.02 g (0.089 mmol) ofpalladium(0) acetate, 5.0 g (11 mmol) of 2-iodo-9,10-diphenylanthracene,and 0.30 g (0.99 mmol) of tris(o-tolyl)phosphine were put into a 200 mLthree-neck flask, and the atmosphere in the flask was substituted withnitrogen. 50 mL of toluene, 20 mL (2 mol/L) of a potassium carbonateaqueous solution, and 10 mL of ethanol were put into the mixture. Themixture was stirred at 100° C. for eight hours to be reacted. After thereaction, toluene was added into the reacted mixture, and thissuspension was washed with saturated sodium hydrogen carbonate water anda saturated saline in this order. An organic layer and an aqueous layerwere separated, and the organic layer was suction-filtrated throughCelite, alumina, and Florisil to obtain a filtrate. The obtainedfiltrate was concentrated, so that a solid substance was obtained.Methanol was added into this solid substance and washed by ultrasonicwave irradiation, so that a solid substance was precipitated. This solidsubstance was collected by suction filtration, so that 4.6 g of a lightyellow powdered solid substance was obtained in a yield of 87% yield.This compound was proved to be 2-(4-bromophenyl)-9,10-diphenylanthraceneby a nuclear magnetic resonance measurement (NMR).

¹H NMR data of 2-(4-bromophenyl)-9,10-diphenylanthracene is shown below.¹H NMR (CDCl₃, 300 MHz): δ=7.33-7.36 (m, 2H), 7.40 (d, J=8.4 Hz, 2H),7.49-7.72 (m, 15H), 7.78 (d, J=9.3 Hz, 1H), 7.85 (d, J=1.5 Hz, 1H).

[Step 1] Synthesis of 4-(carbazol-9-yl)diphenylamine (YGA) (i) Synthesisof N-(4-bromophenyl)carbazole

A synthesis scheme of N-(4-bromophenyl)carbazole is shown in (A-6).

First, a synthesis method of N-(4-bromophenyl)carbazole is described. 56g (0.24 mol) of 1,4-dibromobenzene, 31 g (0.18 mol) of carbazole, 4.6 g(0.024 mol) of copper(I) iodide, 66 g (0.48 mol) of potassium carbonate,and 2.1 g (0.008 mol) of 18-crown-6-ether were put into a 300 mLthree-neck flask, and the atmosphere in the flask was substituted withnitrogen. Then, 8 mL of1,3-dimethyl-3,4,5,6-tetrahydro-2(1H)-pyrimidinone (DMPU) was added, andthe mixture was stirred at 180° C. for six hours. After the reactedmixture was cooled to room temperature, the precipitation was removed bysuction filtration. The filtrate was washed with a diluted hydrochloricacid, a saturated sodium hydrogen carbonate aqueous solution, andsaturated saline in this order. An organic layer was dried withmagnesium sulfate. After the drying, the mixture was filtered naturally,and the obtained filtrate was concentrated, so that an oily substancewas obtained. The oily substance was purified by silica gel columnchromatography (hexane:ethyl acetate=9:1). The obtained solid substancewas recrystallized with a mixed solvent of chloroform and hexane, sothat 21 g of N-(4-bromophenyl)carbazole as a light brown plate-likecrystal was obtained in a yield of 35%. This compound was proved to beN-(4-bromophenyl)carbazole by the nuclear magnetic resonance measurement(NMR).

¹H NMR data of this compound is shown below. ¹H NMR (300 MHz, CDCl₃):δ=8.14 (d, J=7.8 Hz, 2H), 7.73 (d, J=8.7 Hz, 2H), 7.46 (d, J=8.4 Hz,2H), 7.42-7.26 (m, 6H).

(ii) Synthesis of 4-(carbazol-9-yl)diphenylamine (YGA)

A synthesis scheme of 4-(carbazol-9-yl)diphenylamine (YGA) is shown in(A-7).

5.4 g (17.0 mmol) of N-(4-bromophenyl)carbazole obtained in theabove-described step (i), 1.8 mL (20.0 mmol) of aniline, 100 mg (0.17mmol) of bis(dibenzylideneacetone)palladium(0), and 3.9 g (40 mmol) ofsodium tert-butoxide were put into a 200 mL three-neck flask, and theatmosphere in the flask was substituted with nitrogen. Then, 0.1 mL oftri(tert-butyl)phosphine (10 wt % of hexane solution) and 50 mL oftoluene were added to the mixture. The mixture was stirred at 80° C. forsix hours. After reaction, the reacted mixture was filtered throughFlorisil, Celite, and alumina. The filtrate was washed with water andsaturated saline. An organic layer was dried. The mixture was filtered,and the filtrate was concentrated, so that an oily substance wasobtained. The oily substance was purified by silica gel columnchromatography (hexane:ethyl acetate=9:1), so that 4.1 g of4-(carbazol-9-yl)diphenylamine (YGA), which was an object, was obtainedin a yield of 73%. This compound was proved to be4-(carbazol-9-yl)diphenylamine (YGA) by a nuclear magnetic resonancemeasurement (NMR).

¹H NMR data of this compound is shown below. ¹H NMR (300 MHz, DMSO-d₆):δ=8.47 (s, 1H), 8.22 (d, J=7.8 Hz, 2H), 7.44-7.16 (m, 14H), 6.92-6.87(m, 1H).

[Step 4] Synthesis Method of 2YGAPPA

A synthesis scheme of 2YGAPPA is shown in (A-8).

0.51 g (1.1 mmol) of 2-(4-bromophenyl)-9,10-diphenylanthracenesynthesized in Step 2, 0.20 g (2.1 mmol) of tert-BuONa, 0.35 g (1.1mmol) of 4-(carbazol-9-yl)diphenylamine, 0.02 g (0.04 mmol) ofbis(dibenzylideneacetone)palladium(0) were put into a 50 mL three-neckflask, and the atmosphere in the flask was substituted with nitrogen. 10mL of toluene and 0.02 mL of 10 wt % hexane solution oftri(tert-butyl)phosphine were added into the mixture. The mixture washeated and stirred at 80° C. for three hours to be reacted. After thereaction, toluene was added to the reacted mixture, and this suspensionwas suction-filtrated through Florisil, Celite, and alumina. Theobtained filtrate was washed with water and saturated saline and thenmagnesium sulfate was added into an organic layer for drying. Themixture was suction-filtrated to remove magnesium sulfate, and theobtained filtrate was concentrated to obtain a solid substance. Theobtained solid substance was purified using a silica gel columnchromatography. In the silica gel column chromatography, a mixed solventof toluene and hexane (toluene:hexane=1:10) was used as a developingsolvent, and then a mixed solvent of toluene and hexane(toluene:hexane=1:5) was used as a developing solution. The obtainedfraction was concentrated to obtain a solid substance. The solidsubstance was recrystallized with a mixture solvent of dichloromethaneand methanol, so that 0.51 g of a yellow powdered solid substance wasobtained in a yield of 65%. This compound was proved to be2-(4-{N-[4-(carbazol-9-yl)phenyl]-N-phenylamino}phenyl)-9,10-diphenylanthracene(2YGAPPA) by a nuclear magnetic resonance measurement (NMR).

1.4 g of the obtained yellow solid substance was purified by trainsublimation. The sublimation was conducted under a low pressure of 7.0Pa, an argon flow rate of 3 mL/min, at 333° C. for nine hours. 1.2 g ofthe solid substance was obtained in a yield of 86%.

¹H NMR data of the obtained compound is shown below. According to the 1HNMR data, it was found that YGAPPA represented by the above-describedstructural formula (1) was obtained.

¹H NMR data of the obtained compound is shown below. ¹H NMR (CDCl₃, 300MHz): δ=7.06-7.15 (m, 1H), 7.17-7.74 (m, 33H), 7.78 (d, J=9.8 Hz, 1H),7.90 (s, 1H), 8.14 (d, J=7.8 Hz, 2H).

In this manner, 2YGAPPA can be synthesized.

Subsequently, the synthetic method of PCCPA used for the light-emittingelements 4 to 6 will be described because PCCPA is also not a knownsubstance. PCCPA is a substance having the structure represented by thestructural formula (2).

Step 1: Synthesis of 9-phenyl-3,3′-bi(9H-carbazole) (PCC)

2.5 g (10 mmol) of 3-bromocarbazole, 2.9 g (10 mmol) ofN-phenylcarbazole-3-boronate, and 152 mg (0.50 mmol) oftri(ortho-tolyl)phosphine were put into a 200 mL three-neck flask. Theatmosphere in the flask was substituted with nitrogen. 50 mL ofdimethoxyethanol (DME) and 10 mL of potassium carbonate solution (2mol/L) were added to the mixture. The mixture was stirred while pressureis reduced so as to be deaerated. After the deaeration, 50 mg (0.2 mmol)of palladium acetate was added. The mixture was stirred at 80° C. forthree hours under a nitrogen stream. After the stir, about 50 mL oftoluene was added to the mixture and the mixture was stirred for about30 minutes, and then the mixture was washed with water and saturatedsaline in this order. After the washing, an organic layer was dried withmagnesium sulfate. The mixture was naturally filtrated, and the obtainedfiltrate was concentrated, so that an oily substance was obtained. Theobtained oily substance was dissolved in toluene, the solution wasfiltrated through Florisil, alumina, and celite, and the obtainedfiltrate was concentrated, so that 3.3 g of a white solid substance,which was the object, was obtained in a yield of 80%. The synthesisscheme of Step 1 is shown in the following (B-1).

¹H NMR spectrum of the solid substance obtained in above Step 1 wasmeasured by nuclear magnetic resonance measurement. The measurement dataare shown below.

¹H NMR (DMSO-d₆, 300 MHz): (=7.16-7.21 (m, 1H), 7.29-7.60 (m, 8H),7.67-7.74 (m, 4H), 7.81-7.87 (m, 2H), 8.24 (d; J=7.8 Hz, 1H), 8.83 (d,J=7.8 Hz, 1H), 8.54 (d, J=1.5 Hz, 1H), 8.65 (d, J=1.5 Hz, 1H), 11.30 (s,1H).

Step 2: Synthesis of PCCPA

1.2 g (3.0 mmol) of 9-phenyl-10-(4-bromophenyl)anthracene, 1.2 g (3.0mmol) of PCC, and 1.0 g (10 mmol) of tert-BuONa were put into a 100 mLthree-neck flask. The atmosphere in the flask was substituted withnitrogen. 20 mL of toluene and 0.1 mL of tri(tert-butyl)phosphine (10 wt% of hexane solution) were added to the mixture. The mixture was stirredwhile pressure is reduced so as to be deaerated. After the deaeration,96 mg (0:17 mmol) of bis(dibenzylideneacetone)palladium(0) was added tothe mixture. The mixture was refluxed at 110° C. for eight hours under anitrogen stream. After the reflux, about 50 mL of toluene was added tothe mixture, the mixture was stirred for about 30 minutes, and themixture was washed with water and saturated saline in this order. Afterthe washing, an organic layer was dried with magnesium sulfate. Themixture was naturally filtrated, and the obtained filtrate wasconcentrated, so that an oily substance was obtained. The obtained oilysubstance was purified by silica gel column chromatography (hexane(developing solvent):toluene=1:1). The obtained light yellow solidsubstance was recrystallized with chloroform/hexane, so that 1.2 g of alight yellow powdered solid substance of PCCPA, which was an object, wasobtained in a yield of 54%. 2.4 g of the obtained light yellow powderedsolid substance was sublimated and purified by train sublimation. Theconditions for sublimation purification were as follows: the pressurewas 8.7 Pa, the argon gas flow rate was 3.0 mL/min, and the heatingtemperature of PCCPA was 350° C. After the sublimation purification, 2.2g of a light yellow powdered solid substance of PCCPA was obtained in ayield of 94%. The synthesis scheme of Step 2 is shown in the following(B-2).

¹H NMR spectrum of the solid substance obtained in above Step 2 wasmeasured. The measurement data are shown below. According to themeasurement data, it was found that PCCPA represented by theabove-described structural formula (2) was obtained.

¹H NMR (CDCl₃, 300 MHz): δ=7.34-7.91 (m, 32H), 8.27 (d, J=7.2 Hz, 1H),8.31 (d, J=7.5 Hz, 1H), 8.52 (dd, J₁=1.5 Hz, J₂=5.4 Hz, 2H).

The synthesis method of PCBAPA used for the light-emitting elements 7and 8 will be described because PCBAPA is also not a known substance.PCBAPA is a substance having the structure represented by the structuralformula (3).

Step 1: Synthesis of 9-phenyl-9H-carbazole-3-boronic acid

10 g (31 mmol) of 3-bromo-9-phenyl-9H-carbazole was put into a 500 mLthree-neck flask. The atmosphere in the flask was substituted withnitrogen. 150 mL of tetrahydrofuran (THF) was added to the three-neckflask and 3-bromo-9-phenyl-9H-carbazole was dissolved. The solution wascooled to −80° C. Into this solution, 20 mL (32 mmol) of n-butyllithium(1.58 mol/L hexane solution) was dropped with a syringe. After thedropping, the solution was stirred at the same temperature for one hour.After the stir, 3.8 mL (34 mmol) of trimethyl borate was added into thesolution, and while the temperature of the solution was being increasedto room temperature, the solution was stirred for about 15 hours. Afterthe stir, about 150 mL of dilute hydrochloric acid (1.0 mol/L) was addedto the solution and stirred for one hour. After the stir, an aqueouslayer of the mixture was extracted with ethyl acetate and the extractedsolution and an organic layer were washed together with a saturatedsodium hydrogen carbonate aqueous solution. The organic layer was driedwith magnesium sulfate, and then the mixture was naturally filtrated.The obtained filtrate was concentrated, so that a light-brown oilysubstance was obtained. The oily substance was dried with pressurereduced, so that 7.5 g of a light-brown solid substance, which was anobject, was obtained in a yield of 86%. The synthesis scheme of Step 1is shown in the following (C-1).

Step 2: Synthesis of 4-(9-phenyl-9H-carbazol-3-yl)diphenylamine (PCBA)

6.5 g (26 mmol) of 4-bromodiphenylamine, 7.5 g (26 mmol) of9-phenyl-9H-carbazole-3-boronic acid which was synthesized in Step 1,and 400 mg (1.3 mmol) of tri(o-tolyl)phosphine were put into a 500 mLthree-neck flask. The atmosphere in the flask was substituted withnitrogen. 100 mL of toluene, 50 mL of ethanol, and 14 mL of potassiumcarbonate solution (0.2 mol/L) were added to the mixture. The mixturewas stirred under low pressure so as to be deaerated. After thedeaeration, 67 mg (30 mmol) of palladium(II) acetate was added. Themixture was refluxed at 100° C. for 10 hours. After the reflux, anaqueous layer of the mixture was extracted with toluene and theextracted solution and an organic layer were washed together with asaturated saline. The organic layer was dried with magnesium sulfate,and then the mixture was naturally filtrated. The obtained filtrate wasconcentrated, so that a light-brown oily substance was obtained. Theobtained oily substance was purified by silica gel column chromatography(hexane:toluene=4:6 (developing solvent). After the purification, theobtained white solid substance was recrystallized with a mixed solventof dichloromethane and hexane, so that 4.9 g of a white solid substanceof PCBA was obtained in a yield of 45%. The synthesis scheme of Step 2is shown in the following (C-2).

Step 3: Synthesis of PCBAPA

7.8 g (12 mmol) of 9-(4-bromophenyl)-10-phenylanthracene, 4.8 g (12mmol) of PCBA, and 5.2 g (52 mmol) of sodium tert-butoxide were put intoa 300 mL three-neck flask. The atmosphere in the flask was substitutedby nitrogen. 60 mL of toluene and 0.30 mL of tri(tert-butyl)phosphine(10 wt % of hexane solution) were added to the mixture. The mixture wasstirred under low pressure so as to be deaerated. After the deaeration,136 mg (0.24 mmol) of bis(dibenzylideneacetone)palladium(O) was added tothe mixture. The mixture was stirred at 100° C. for three hours. Afterthe stir, about 50 mL of toluene was added to the mixture, and then themixture was suction-filtrated through Celite (produced by Wako PureChemical Industries, Ltd., Catalog No. 531-16855), alumina, and Florisil(produced by Wako Pure Chemical Industries, Ltd., Catalog No.540-00135). The obtained filtrate was concentrated, so that a yellowsolid substance was obtained. The solid substance was recrystallizedwith a mixed solvent of toluene and hexane, so that 6.6 g of a lightyellow solid substance of PCBAPA, which was an object, was obtained in ayield of 75%. 3.0 g of the obtained light yellow powdered solidsubstance was sublimated and purified by train sublimation. Theconditions for sublimation purification were as follows: the pressurewas 8.7 Pa, the argon gas flow rate was 3.0 mL/min, and the heatingtemperature of PCBAPA was 350° C. After the sublimation purification,2.7 g of a light yellow powdered solid substance of PCBAPA was obtainedin a yield of 90%. The synthesis scheme of Step 3 is shown in thefollowing (C-3).

¹H NMR spectrum of the solid substance obtained in above Step 3 wasmeasured. The measurement data are shown below. According to themeasurement result, it was found that PCBAPA represented by theabove-described structural formula (3) was obtained.

¹H NMR (CDCl₃, 300 MHz): δ=7.08-7.14 (m, 31H), 7.32-7.72 (m, 33H), 7.88(d, J=7.8 Hz, 2H), 8.19 (d, J=7.8 Hz, 1H), 8.37 (d, J=1.5 Hz, 1H).

This application is based on Japanese Patent Application serial No.2007-250512 filed with Japan Patent Office on Sep. 27, 2007, the entirecontents of which are hereby incorporated by reference.

What is claimed is:
 1. A light-emitting device comprising: a substrate;a transistor over the substrate; and a light-emitting elementelectrically connected the transistor, wherein the light-emittingelement comprising: an anode electrically connected to one of a sourceelectrode and a drain electrode of the transistor; a first layer overthe anode; a second layer over the first layer; a third layer over thesecond layer; and a cathode over the third layer, wherein the firstlayer comprises a first organic compound and a second organic compound,wherein the second layer comprises a third organic compound and a fourthorganic compound, wherein the third layer comprises the first organiccompound and a fifth organic compound, wherein the first organiccompound and the third organic compound have a light-emitting property,wherein a color of light emitted from the first organic compound isblue, and wherein a color of light emitted from the third organiccompound is yellow.
 2. The light-emitting device according to claim 1,wherein the light-emitting element further comprises a hole-transportlayer between the anode and the first layer.
 3. The light-emittingdevice according to claim 1, wherein the light-emitting element furthercomprises an electron-transporting layer provided between the thirdlayer and the cathode.
 4. The light-emitting device according to claim1, wherein the fifth organic compound has an electron-transportproperty.
 5. The light-emitting device according to claim 1, wherein thesecond organic compound and the fourth organic compound have the sametransport property.
 6. The light-emitting device according to claim 1,wherein the third organic compound comprises a material which emitsphosphorescence.
 7. The light-emitting device according to claim 1,wherein the first organic compound and the third organic compound areused as an emission center substance, and wherein the second organiccompound, the fourth organic compound, and the fifth organic compoundare used as a host material.
 8. The light-emitting device according toclaim 1, wherein a peak wavelength of light emitted from the firstorganic compound is in a range of 400 nm to 480 nm, and wherein a peakwavelength of light emitted from the third organic compound is in arange of 540 nm to 600 nm.
 9. The light-emitting device according toclaim 1, wherein the anode comprises indium tin oxide, and wherein thecathode comprises aluminum.
 10. The light-emitting device according toclaim 1, wherein the transistor is configured to control a currentflowing in the light-emitting element.
 11. A light-emitting devicecomprising: a substrate; a transistor over the substrate; and alight-emitting element electrically connected the transistor, whereinthe light-emitting element comprising: an anode electrically connectedto one of a source electrode and a drain electrode of the transistor; afirst layer over the anode; a second layer over the first layer; a thirdlayer over the second layer; and a cathode over the third layer, whereinthe first layer comprises a first organic compound and a second organiccompound, wherein the second layer comprises a third organic compoundand a fourth organic compound, wherein the third layer comprises thefirst organic compound and a fifth organic compound, wherein the firstorganic compound and the third organic compound have a light-emittingproperty, wherein a peak wavelength of light emitted from the firstorganic compound is shorter than a peak wavelength of light emitted fromthe third organic compound, and wherein a color of light emitted fromthe first organic compound and a color of light emitted from the thirdorganic compound are complementary colors.
 12. The light-emitting deviceaccording to claim 11, wherein the light-emitting element furthercomprises a hole-transport layer between the anode and the first layer.13. The light-emitting device according to claim 11, wherein thelight-emitting element further comprises an electron-transporting layerprovided between the third layer and the cathode.
 14. The light-emittingdevice according to claim 11, wherein the fifth organic compound has anelectron-transport property.
 15. The light-emitting device according toclaim 11, wherein the second organic compound and the fourth organiccompound have the same transport property.
 16. The light-emitting deviceaccording to claim 11, wherein the third organic compound comprises amaterial which emits phosphorescence.
 17. The light-emitting deviceaccording to claim 11, wherein the first organic compound and the thirdorganic compound are used as an emission center substance, and whereinthe second organic compound, the fourth organic compound, and the fifthorganic compound are used as a host material.
 18. The light-emittingdevice according to claim 11, wherein the peak wavelength of lightemitted from the first organic compound is in a range of 400 nm to 480nm, and wherein the peak wavelength of light emitted from the thirdorganic compound is in a range of 540 nm to 600 nm.
 19. Thelight-emitting device according to claim 11, wherein the anode comprisesindium tin oxide, and wherein the cathode comprises aluminum.
 20. Thelight-emitting device according to claim 11, wherein the transistor isconfigured to control a current flowing in the light-emitting element.